That happened to me once because I put a bad block on the site and even after removing it via PHP-MyAdmin and everything, it still wouldn't load.

Dump every temp file you can. It worked for me great. Even spead up the computer, lol.

I use CCleaner from http://ccleaner.com

they even offer Secure File Deletion up to 7 passes.

(now I'm sounding like an advertisement. sorry)