So I use PHP in some areas of our site (quick hacks or 3rd party stuff) and in order to put php4 on my Debian Woody system, I gotta go w/ a backport
Anyway, I had to restore a backup of both libphp4.so and 500mod_php4.info and that seemed to work. But add to the mix my browser was caching stuff, so I sometimes didn't think it was working when it could have been working.
Man, that's a good cardio workout, to have your production server go down and it's your fault.
Ok, so lesson learned: don't upgrade your server software in the middle of the day. I know you're prolly like "D'uh!", but it's just so tempting sometimes to 'apt-get -qyu update/upgrade'... never has hurt me before. But now I have a vicious scar and have learned my lesson.