This issue applies to many (if not most) of the 2008 products. The good news is that Autodesk just released a hotfix that fixes the error some users are getting after applying a service pack. If you see:
Fatal Error: Unhandled Access Violation Reading 0x0000 Exception at 61b351d6h
Download this hotfix to see if it resolves your issue. If not, call the Avatech Support Center 800-808-7645.
For more information on this issue check out the Autodesk page http://usa.autodesk.com/getdoc/id=DL10189158.