Thank you for your post.
From the limited information, it is difficult to determine where the problem lies. However, let's try a few things...
Create a new user account on your computer. Log into the new user account and launch FileMaker Pro 8.5. Try to open a file. If this works, then your original user account may be damaged. If you still get the unresponsiveness or crash, then uninstall and reinstall FileMaker Pro 8.5 and try again. If this still doesn't work, then run "msconfig" and stop all non-Microsoft services. Launch FileMaker Pro 8.5 again and try again. If this still doesn't work, then there is something in the system that is conflicting with FileMaker Pro 8.5 and you'll need to do some further sleuthing.
TSGAl - Thank you for your reply. Your suggestion was right on. There was a problem in the computer itself. Updated to Service pack 3, ran some diagnostics and FMP ran fine from there on. - Dave T.