I have this since a few days on BB, firefox and chrome (different pc).
There is something that must have been touched a few days ago.
Rectify this, and problem is solved.
Just try restoring the php, html, etc (not sql) from a week ago, and see what it does.
(I'm sure with such a site you have auto-backups in place, or its being manually being 'backuped' every few days at least)