Fatal Error: Unhandled Access Violation Reading 0x4cd00159 Exception at 4cd00159h

My company is currently in a transition phase from Acad 2006 to 2010. Currently only 2 users have 2010 on their machine while we do testing. One users computer (Mine) works fine, the other get this fatal error message when closing a drawing. I googled the error and tried a few options that it gave me. I unchecked the "validate signature" option, and that had no effect. I also checked their computer to see that they had the latest microsoft .net 3.5 sp1 (which they do). So now I thought I would probe the minds of this forum for some answers. I am going to try and reinstall 2010 onto their machine and see if that helps. But I would still like imput from this community. Thanks for your help.

Let's be clear. We are talking about AutoCAD MEP 2010 are we not?

Yes, Acad MEP 2010.

All systems were tested using the same drawing so as to eliminate the possibility that a severly corrupted drawing was the cause of the problem?

Yes, I was able to work on the drawings with no problem, but the other employee still had the fatal error. They are able to work on the drawings, just when they close it after they are done, thats when the fatal error occurs.

Possible network related problem? All "paths" have been checked/verified?

Which "paths" specifically? There are alot of paths :-P

The path to where the drawing is saved.

We use Proarc for drawing storage. The drawing is stored on our server, then we "check them out" and they are put onto our local machine to be edited. The path to the drawing is automatically created when the drawing is "check out" of Proarc.