7
Ok, after two or three days of this crap, I fixed it.
First, I had to hack up recovery.php in order to get the debug to work (stupid PM using the same database key). Then, once I got a bit better understanding of what was going on, I tried playing around with some different themes (as per Juliette's advice) and found that the default one and my custom theme wouldnt work, but the other themes would.
So I figured something about the themes were corrupt, so I uploaded a fresh copy of my custom theme (I dont happen to have a copy of the default one here) and that worked, but some of the modules (specifically the News module) didnt work right.
So I went into the templates and deleted all the ones being used by the afflicted module and regenerated them. Now everything seems to work fine.
Still not sure what caused the problem in the first place, but it works now.