I made some simple changes to some forms and I rebuilt a new exe and redistribute it to the clients machines.   The application runs fine on my development machine.  But when I try to run it on the client machines it gives me the errors below.  From what I can tell through additional testing, the errors are occuring for ALL combo boxes I am populating using the BO with the PopulationDataSourceSettings/PopulationType properties.   What is really strange is all of these forms and combo boxes and BOs have been working fine for a long time!?!?   Help?

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Type 'CMPR.LocationsViewBO' could not be found in the referenced assemblies.
  Exception (Exception): Source="MicroFour StrataFrame Base"; Target=null; Tag=null;
    Message = "Type 'CMPR.LocationsViewBO' could not be found in the referenced assemblies."
    InnerException (FileNotFoundException): Source="mscorlib"; Target=null; Tag=null;
      Message = "Could not load file or assembly 'DevExpress.XtraReports.v8.1, Version=8.1.1.0, Culture=neutral, PublicKeyToken=9b171c9fd64da1d1' or one of its dependencies. The system cannot find the file specified."
      StackTrace =
          "   at System.Reflection.Assembly.nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection)
             at System.Reflection.Assembly.InternalLoad(AssemblyName assemblyRef, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection)
             at System.Reflection.Assembly.Load(AssemblyName assemblyRef)
             at MicroFour.StrataFrame.Tools.Common.GetTypeFromReferencedAssemblies(String TypeName)"
      FileName = "DevExpress.XtraReports.v8.1, Version=8.1.1.0, Culture=neutral, PublicKeyToken=9b171c9fd64da1d1"
      FusionLog =
          "WRN: Assembly binding logging is turned OFF.
          To enable assembly bind failure logging, set the registry value [HKLM\Software\Microsoft\Fusion!EnableLog] (DWORD) to 1.
          Note: There is some performance penalty associated with assembly bind failure logging.
          To turn this feature off, remove the registry value [HKLM\Software\Microsoft\Fusion!EnableLog].
          "
  Environment: ThreadIdentity="" DateTime=["2008-05-01 11:41:17.099"] ThreadName=null WindowsIdentity="STRUSS\JPagley" ThreadId="1" DomainName="cmpr.exe" OSVersion=["Microsoft Windows NT 5.0.2195 Service Pack 4"] MachineName="INVENTORY"
    UserName="JPagley"
  Remaining Stack Trace  - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    at MicroFour.StrataFrame.Tools.Common.GetTypeFromReferencedAssemblies(String TypeName)
    at MicroFour.StrataFrame.UI.Windows.Forms.ListControl.PopulateComboFromBusinessObject(IListControl lstControl, Object[] Parameters)
    at MicroFour.StrataFrame.UI.Windows.Forms.ListControl.PopulateCombo(Control lstControl, Object[] Parameters)
    at MicroFour.StrataFrame.UI.Windows.Forms.DevEx.ComboBoxEdit.PopulateCombo(Object[] Parameters)
    at MicroFour.StrataFrame.UI.Windows.Forms.DevEx.ComboBoxEdit.Requery()
    at MicroFour.StrataFrame.UI.Windows.Forms.DevEx.ComboBoxEdit.InitializeObject()
    at MicroFour.StrataFrame.UI.Windows.Forms.BaseForm.InitializeFormLoadObjects()
    at MicroFour.StrataFrame.UI.Windows.Forms.BaseForm.OnLoad(EventArgs e)
    at System.Windows.Forms.Form.OnCreateControl()
    at System.Windows.Forms.Control.CreateControl(Boolean fIgnoreVisible)
    at System.Windows.Forms.Control.CreateControl()
    at System.Windows.Forms.Control.WmShowWindow(Message& m)
    at System.Windows.Forms.Control.WndProc(Message& m)
    at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
    at System.Windows.Forms.ContainerControl.WndProc(Message& m)
    at System.Windows.Forms.Form.WmShowWindow(Message& m)
    at System.Windows.Forms.Form.WndProc(Message& m)
    at System.Windows.Forms.Control.ControlNativewindow.OnMessage(Message& m)
    at System.Windows.Forms.Control.ControlNativewindow.WndProc(Message& m)
    at System.Windows.Forms.Nativewindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

• Old assemblies are still in the GAC or on disk
• New assemblies did not get distributed
• Permission issues prevents the assemblies from being updated
• Multiple versions of the same assembly are in the GAC (i.e. MSIL, x86 builds)

It is going to be something along these lines, so you might start with the above "gotchas" and go from there.

As you suggested, I found I was missing an .dll file.  As always, excellent support and help.  Thanks!