sounds alot like the recent wave of .NET Framework issues that have
caused issues with alot of Adsk products.
I don't have a link to provide here, but someone within one of the Adsk
forums posted a step by step process of how to go about first
uninstalling all versions of .NET Framework, running a .NET Framework
cleanup ultility from MS, then reinstalling all versions of .NET
Framework starting with 1.0, then 2 then 3 (and any and all updates or
versions inbetween)
I dug a little and here's the link;
http://discussion.autodesk.com/forums/thread.jspa?threadID=714082&tstart=0
Hopefully the link comes thru ok and doesn't get munged like some have
recently.
look for a reply from dzutski who posts the step by step method of
fixing a corrupt .NET Framework install.
HTH