Thanks for the info. I tried it on one of the clients in question, but it didn't help. I then remember a tool that I have used several times in the past:
http://www.tweaking.com/content/page/windows_repair_all_in_one.html
I tried this on the client computer, repaired most of the registry using the tool, rebooted and the computer scanned fine after that. Thanks again for the help!