Did you make something against google TOS ? For example a friend of mine made spam and now. He had PR4 now he has pr0 like yours. But I think you don't make spam . So it'S interesting. Can you write website name ?
Nevermine the PR4 is back again. Its weird the PR4 was gone the whole day, but now that I check again, its back.
Sorry to hear that, but it has to do with the quality of the links coming into your site. Their quality dropped, and so your PR did, too. (prilep, the PR update finished up about two weeks ago. )
Different PRs are shown for various datacenters also, refer to the following PR checker for an overview: http://livepr.raketforskning.com/
i'm having the same problem with you . my backlinks are staying for that site but its pr has gone from 4 to 0 . i did not find an answer too