The symptom of this bug is that as soon as the issue occurs, the user is no longer able to tab between fields in any Microsoft Dynamics GP window.
The nature of the bug is a combination of a .NET Framework application window (typically a Dynamics GP Add-in) displayed as a modal window and having VBA active in Dynamics. After the Add-in window is closed, the issue prevents the user from being able to tab between fields in any Microsoft Dynamics GP window until they exit Microsoft Dynamics GP.
The reason for the Microsoft.Dexterity.Support.FilterEvents.dll is to resolve MBS Great Plains bug 46619 in all versions of Microsoft Dynamics GP 10.0.
The problem area is within the event processing loop which controls all aspects of Dynamics including the code and in the user interface. When an Add-in window is opened as a modal window and then closed, the Dynamics.exe runtime processes does not correctly handle the tab keystrokes. The keystrokes that move the focus instead move to the first field on the window and not from field to field in the typical tab sequence.
In order to lessen risk to the Dynamics GP community, the solution is implemented as an Add-in assembly. This assembly is basically the same code that would typically go into the Dynamics.exe runtime engine, it is just packaged as an external application.
The resolve this issue, download the MBSGreatPlains_46619.zip file and follow the installation instructions contained in the compressed (.zip) file.