What Version of AutoCad are you using.
The reason I ask is that We are using 2005LT, and I frequently have 'Errors' when I shut down AutoCad. It doesn't affect the closing dwg, and AutoCad opens again without problems, but it is annoying to get the AutoCad Error message. I have re-installed several times, still there.
It's annoying, but not worth spending many hours trying to fix.
I just figure that they changed something in their shutdown process, since I haven't had the problem with previous releases.
craigr