This only happened for the first time a couple of days ago, and I didn't make any changes or additions to my system recently.
What I tried to do to fix it so far:
First I checked for viruses or spyware that could clog up Photoshop, then I deleted the preferences file and defragmented my hard drive (for good measure). When that didn't work I re-installed Photoshop. After that, I asked a friend to help and he got rid of a few processes that he said were not needed. We thought that fixed it but in only two days it's back!
Any ideas? I can ask a few more people to try to fix it, but I'll be out of friends soon and I need my Photoshop.