404 Category Errors since 3.3

The title explains it all. Since updating to 3.3 (I just noticed it) my category urls return 404 errors. Not sure why. I’ve tried disabling all widgets/plugins and changing themes. No effect.

I read somewhere that deleting the database and re-importing the posts fixes the problem, but I don’t know how to do that. So I’m lost.

Need any other information? Any help would be greatly appreciated. Thanks guys.