Error: Explorer! when opening folders

This problem has progressed from irritating to serious...

When I click on any folder (ie My Documents, music, etc) a small error box pops up saying "Explorer!". I must click OK before the folder will open.

When this happens in My Documents, after about 5 seconds it tells me an error has occured and the program must be shutdown. This restarts my entire window explorer. If I choose to send an error report, my computer freezes completely halfway through everytime and must be forcibly restarted.

I have Norton Antivirus and it doesn't detect a virus. I also have AdAware SE. Any idea what the problem is?

Thanks, Madison