I participate in a lot of forums. This is the only one that a Message from Microsoft comes up on the screen and freezes up my computer. Please help me out. I cannot move from one thread/post to another. Very frustrated.

1) delete your browser cache, malware could be stuck there and executing.
and/or
2) malwarebytes, the free version

If it's what I think it is, it's not from this site.

Anything better than CCleaner for clearing cache and registry stuff?

CCleaner keeps things humming here, don't know what more I'd want. Hint. When you run CCleaner (free version) it starts two tasks. One remains active when you close the program and periodically throws up a nag screen. You can go to task manager, kill it, and no more nag screens.