I thought I'd relate my experince incase anyone here is (or will be in the future) going through something similar.
After the last PR update (the one like a month ago) one of my sites had a PR of 0 on the index page. (down from 5) I couldn't figure out why. I still was linking to it from about 8 other PR 5 sites, not to mention incoming links from other people's sites. When searching for my url or backlinks in Google nothing turned up. I couldn't figure it out because I knew I had done nothing wrong to get banned. Another weird thing was that my subpages all still had PR, and they have absolutely no backlinks except for from the PR0 index page.
Well, I waited a month and PR updated again and my PR is back and so are my backlinks.

I'm guessing it was some kind of error.