With the latest version this error occurs on a regular basis just by browsing through the main grid. There is no definite pattern like a certain number of clicks in the grid but it's repeatable without problems. 
 
Details of Exception - in German, sorry:
************** Ausnahmetext **************
System.IndexOutOfRangeException: Der Index war außerhalb des Arraybereichs.
   bei DevExpress.XtraBars.Docking.Paint.DrawTabPanelArgs.GetTabArgs(Int32 index)
   bei DevExpress.XtraBars.Docking.Paint.DockElementsPainter.DrawTabPanel(DrawTabPanelArgs args)
   bei DevExpress.XtraBars.Docking.Helpers.DockLayout.DrawTabPanel(DockElementsPainter painter)
   bei DevExpress.XtraBars.Docking.Helpers.DockLayout.Draw(PaintEventArgs e, DockElementsPainter painter)
   bei DevExpress.XtraBars.Docking.DockPanel.OnPaint(PaintEventArgs e)
   bei System.Windows.Forms.Control.PaintWithErrorHandling(PaintEventArgs e, Int16 layer)
   bei System.Windows.Forms.Control.WmPaint(Message& m)
   bei System.Windows.Forms.Control.WndProc(Message& m)
   bei System.Windows.Forms.ScrollableControl.WndProc(Message& m)
   bei System.Windows.Forms.ContainerControl.WndProc(Message& m)
   bei DevExpress.XtraBars.Docking.ZIndexControl.WndProc(Message& m)
   bei DevExpress.XtraBars.Docking.DockPanel.WndProc(Message& m)
   bei System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   bei System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   bei System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
************** Geladene Assemblys **************
mscorlib
    Assembly-Version: 4.0.0.0.
    Win32-Version: 4.0.30319.296 (RTMGDR.030319-2900).
    CodeBase: file:///C:/Windows/Microsoft.NET/Framework/v4.0.30319/mscorlib.dll.
----------------------------------------
eXtreme Movie Manager
    Assembly-Version: 8.0.4.3.
    Win32-Version: 8.0.4.3.
    CodeBase: file:///C:/Program%20Files%20(x86)/eXtreme/Movie%20Manager%208/eXtreme%20Movie%20Manager.exe.
----------------------------------------
Microsoft.VisualBasic
    Assembly-Version: 10.0.0.0.
    Win32-Version: 10.0.30319.1 built by: RTMRel.
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/Microsoft.VisualBasic/v4.0_10.0.0.0__b03f5f7f11d50a3a/Microsoft.VisualBasic.dll.
----------------------------------------
System
    Assembly-Version: 4.0.0.0.
    Win32-Version: 4.0.30319.1001 built by: RTMGDR.
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System/v4.0_4.0.0.0__b77a5c561934e089/System.dll.
----------------------------------------
System.Core
    Assembly-Version: 4.0.0.0.
    Win32-Version: 4.0.30319.233 built by: RTMGDR.
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Core/v4.0_4.0.0.0__b77a5c561934e089/System.Core.dll.
----------------------------------------
System.Windows.Forms
    Assembly-Version: 4.0.0.0.
    Win32-Version: 4.0.30319.1001 built by: RTMGDR.
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Windows.Forms/v4.0_4.0.0.0__b77a5c561934e089/System.Windows.Forms.dll.
----------------------------------------
System.Drawing
    Assembly-Version: 4.0.0.0.
    Win32-Version: 4.0.30319.1001 built by: RTMGDR.
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Drawing/v4.0_4.0.0.0__b03f5f7f11d50a3a/System.Drawing.dll.
----------------------------------------
System.Runtime.Remoting
    Assembly-Version: 4.0.0.0.
    Win32-Version: 4.0.30319.1 (RTMRel.030319-0100).
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Runtime.Remoting/v4.0_4.0.0.0__b77a5c561934e089/System.Runtime.Remoting.dll.
----------------------------------------
System.Configuration
    Assembly-Version: 4.0.0.0.
    Win32-Version: 4.0.30319.1 (RTMRel.030319-0100).
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Configuration/v4.0_4.0.0.0__b03f5f7f11d50a3a/System.Configuration.dll.
----------------------------------------
System.Xml
    Assembly-Version: 4.0.0.0.
    Win32-Version: 4.0.30319.233 built by: RTMGDR.
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Xml/v4.0_4.0.0.0__b77a5c561934e089/System.Xml.dll.
----------------------------------------
DevExpress.XtraEditors.v12.1
    Assembly-Version: 12.1.8.0.
    Win32-Version: 12.1.8.0.
    CodeBase: file:///C:/Program%20Files%20(x86)/eXtreme/Movie%20Manager%208/DevExpress.XtraEditors.v12.1.DLL.
----------------------------------------
DevExpress.Utils.v12.1
    Assembly-Version: 12.1.8.0.
    Win32-Version: 12.1.8.0.
    CodeBase: file:///C:/Program%20Files%20(x86)/eXtreme/Movie%20Manager%208/DevExpress.Utils.v12.1.DLL.
----------------------------------------
DevExpress.Data.v12.1
    Assembly-Version: 12.1.8.0.
    Win32-Version: 12.1.8.0.
    CodeBase: file:///C:/Program%20Files%20(x86)/eXtreme/Movie%20Manager%208/DevExpress.Data.v12.1.DLL.
----------------------------------------
System.Data
    Assembly-Version: 4.0.0.0.
    Win32-Version: 4.0.30319.237 (RTMGDR.030319-2300).
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_32/System.Data/v4.0_4.0.0.0__b77a5c561934e089/System.Data.dll.
----------------------------------------
DevExpress.BonusSkins.v12.1
    Assembly-Version: 12.1.8.0.
    Win32-Version: 12.1.8.0.
    CodeBase: file:///C:/Program%20Files%20(x86)/eXtreme/Movie%20Manager%208/DevExpress.BonusSkins.v12.1.DLL.
----------------------------------------
System.Numerics
    Assembly-Version: 4.0.0.0.
    Win32-Version: 4.0.30319.1 built by: RTMRel.
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Numerics/v4.0_4.0.0.0__b77a5c561934e089/System.Numerics.dll.
----------------------------------------
System.Data.resources
    Assembly-Version: 4.0.0.0.
    Win32-Version: 4.0.30319.1 (RTMRel.030319-0100).
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Data.resources/v4.0_4.0.0.0_de_b77a5c561934e089/System.Data.resources.dll.
----------------------------------------
CustomMarshalers
    Assembly-Version: 4.0.0.0.
    Win32-Version: 4.0.30319.1 (RTMRel.030319-0100).
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_32/CustomMarshalers/v4.0_4.0.0.0__b03f5f7f11d50a3a/CustomMarshalers.dll.
----------------------------------------
DevExpress.XtraBars.v12.1
    Assembly-Version: 12.1.8.0.
    Win32-Version: 12.1.8.0.
    CodeBase: file:///C:/Program%20Files%20(x86)/eXtreme/Movie%20Manager%208/DevExpress.XtraBars.v12.1.DLL.
----------------------------------------
mscorlib.resources
    Assembly-Version: 4.0.0.0.
    Win32-Version: 4.0.30319.1 (RTMRel.030319-0100).
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/mscorlib.resources/v4.0_4.0.0.0_de_b77a5c561934e089/mscorlib.resources.dll.
----------------------------------------
DevExpress.XtraGrid.v12.1
    Assembly-Version: 12.1.8.0.
    Win32-Version: 12.1.8.0.
    CodeBase: file:///C:/Program%20Files%20(x86)/eXtreme/Movie%20Manager%208/DevExpress.XtraGrid.v12.1.DLL.
----------------------------------------
DevExpress.XtraPrinting.v12.1
    Assembly-Version: 12.1.8.0.
    Win32-Version: 12.1.8.0.
    CodeBase: file:///C:/Program%20Files%20(x86)/eXtreme/Movie%20Manager%208/DevExpress.XtraPrinting.v12.1.DLL.
----------------------------------------
DevExpress.Printing.v12.1.Core
    Assembly-Version: 12.1.8.0.
    Win32-Version: 12.1.8.0.
    CodeBase: file:///C:/Program%20Files%20(x86)/eXtreme/Movie%20Manager%208/DevExpress.Printing.v12.1.Core.DLL.
----------------------------------------
System.Web
    Assembly-Version: 4.0.0.0.
    Win32-Version: 4.0.30319.272 built by: RTMGDR.
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_32/System.Web/v4.0_4.0.0.0__b03f5f7f11d50a3a/System.Web.dll.
----------------------------------------
System.Windows.Forms.resources
    Assembly-Version: 4.0.0.0.
    Win32-Version: 4.0.30319.1 built by: RTMRel.
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Windows.Forms.resources/v4.0_4.0.0.0_de_b77a5c561934e089/System.Windows.Forms.resources.dll.
----------------------------------------
Interop.DexterLib
    Assembly-Version: 1.0.0.0.
    Win32-Version: 1.0.0.0.
    CodeBase: file:///C:/Program%20Files%20(x86)/eXtreme/Movie%20Manager%208/Interop.DexterLib.DLL.
----------------------------------------
System.Transactions
    Assembly-Version: 4.0.0.0.
    Win32-Version: 4.0.30319.1 (RTMRel.030319-0100).
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_32/System.Transactions/v4.0_4.0.0.0__b77a5c561934e089/System.Transactions.dll.
----------------------------------------
System.EnterpriseServices
    Assembly-Version: 4.0.0.0.
    Win32-Version: 4.0.30319.1 (RTMRel.030319-0100).
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_32/System.EnterpriseServices/v4.0_4.0.0.0__b03f5f7f11d50a3a/System.EnterpriseServices.dll.
----------------------------------------
WindowsBase
    Assembly-Version: 4.0.0.0.
    Win32-Version: 4.0.30319.298 built by: RTMGDR.
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/WindowsBase/v4.0_4.0.0.0__31bf3856ad364e35/WindowsBase.dll.
----------------------------------------
Anonymously Hosted DynamicMethods Assembly
    Assembly-Version: 0.0.0.0.
    Win32-Version: 4.0.30319.296 (RTMGDR.030319-2900).
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_32/mscorlib/v4.0_4.0.0.0__b77a5c561934e089/mscorlib.dll.
----------------------------------------
Accessibility
    Assembly-Version: 4.0.0.0.
    Win32-Version: 4.0.30319.1 built by: RTMRel.
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/Accessibility/v4.0_4.0.0.0__b03f5f7f11d50a3a/Accessibility.dll.
----------------------------------------
DevExpress.XtraLayout.v12.1
    Assembly-Version: 12.1.8.0.
    Win32-Version: 12.1.8.0.
    CodeBase: file:///C:/Program%20Files%20(x86)/eXtreme/Movie%20Manager%208/DevExpress.XtraLayout.v12.1.DLL.
----------------------------------------
Microsoft.VisualBasic.resources
    Assembly-Version: 10.0.0.0.
    Win32-Version: 10.0.30319.1 built by: RTMRel.
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/Microsoft.VisualBasic.resources/v4.0_10.0.0.0_de_b03f5f7f11d50a3a/Microsoft.VisualBasic.resources.dll.
----------------------------------------
System.resources
    Assembly-Version: 4.0.0.0.
    Win32-Version: 4.0.30319.1 built by: RTMRel.
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.resources/v4.0_4.0.0.0_de_b77a5c561934e089/System.resources.dll.
----------------------------------------
Microsoft.mshtml
    Assembly-Version: 7.0.3300.0.
    Win32-Version: 7.0.3300.0.
    CodeBase: file:///C:/Windows/assembly/GAC/Microsoft.mshtml/7.0.3300.0__b03f5f7f11d50a3a/Microsoft.mshtml.dll.
----------------------------------------
System.Drawing.resources
    Assembly-Version: 4.0.0.0.
    Win32-Version: 4.0.30319.1 built by: RTMRel.
    CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Drawing.resources/v4.0_4.0.0.0_de_b03f5f7f11d50a3a/System.Drawing.resources.dll.
----------------------------------------
Essentially, it looks like this: all docked windows are loosing their tab controls (it happened also to the tabbed details view / edit view window, I just didn't add a screenshot for this):

So, since I have three docked windows with tabs (left side: tree / mini stat + Front / Back cover; right side Details / Quick Edit) the error occurs three times per session. Once I've lost all three tab controls it seems "OK" for XMM ... but not for me. 
 
Maybe it's the same like here: http://www.binaryworks.it/forum/topic.asp?TOPIC_ID=10467 - but it didn't happen with 8.0.4.2.