yes because Search Engines are now following quality content. only site's with quality content with quality backlinks got PageRank .. Thanks God We were on PR2 and Still PR2 . No profit , no loss...
I think it will be wise to re-write the content of your website with some unique & useful information. Continue your Off Page optimization also.
it was fake PR6 or something, i don't believe, that from real PR 6 you can get to PRzero, i had PR6 and now i am sitting already second update on PR5. and i know why, some of my powerful backlinks got lower PR as well.