My site goes down every time I do something in my admin. If I restore the files from the previous day, all is well again. But then if I even look at something in my admin, the whole site goes down again. I have tried to upgrade my database with the zc_install but I get the following:

Problem Detected

Sorry, a problem has been detected.

This installer needs to be able to start a PHP session in order to complete installation.

I don't think it's a timeout problem. The cache folder permissions are right. And my host accepts php. I have been adding on mods recently and I think one of them messed me up, but I didn't discover this problem until it was too late to restore my database...it's been too long and the restoreable databases aren't old enough to roll this back. Please help! What did I do????