Hummm...I'm now thinking that my host provider might have uploaded some stuff and it got screw up.
I'm not able to access phpMyAdmin either:
phpMyAdmin - Error
Error during session start; please check your PHP and/or webserver log file and configure your PHP installation properly. Also ensure that cookies are enabled in your browser.
session_start(): open(SESSION_FILE, O_RDWR) failed: Permission denied (13)
Is it possible that a settings come to a default value somewhere?