I have a few sites that I run. One was PR3 one was a PR2 and one I just put up. I checked into the sites last week and all sites now have a PR of 0.
All my content is unique.
I have all my sites on one server, and the only thing I can think is that a site was peanilized for some reason and because all the sites are add-on domains they all got peanilized.
Does this make any sense?