Page Rank issue?

Hi everyone, i have a domain and it was PR0 i blasted some backlinks and i got 500 bing at 388 yahoo backlinks, no google backlinks at all, and then at the latest google PR update i got PR1, i have continue to build backlinks now i have 2k bing and 1k yahoo backlinks indexed, but today when i checked my site it says PR0, wtf, i checked with 5 different PR checker and all shows PR0 so thats not the problem, does someone have a answer to this, does google take your PR even its not the update time its not like i know when it is, or i dont know?