Demoted by Google, Why? How do I get out?

PR5 with several good backlinks and content

[GodLikeLotus]

Its now been 6 months since a site I run sank in Google's SERPS. The site was getting around 3000 unique visitors from Google and then BANG, site demoted to bottom of the class. All 400+ pages remained in the index, just lost all ratings, page 50+, useless.

I have battled hard to gain good quality backlinks, improved the overall navigation of the site and added more unique content. Have links from DMOZ and Yahoo with great descriptions and decent PR's, 5 and 7.

I guess its like a game of chess except my oponent takes rather a long time to make moves these days. Oh how I wish is was like the good old days when you could just look at the full-moon and know that Google is about to make its next move.

Come on Google, do a big update, I promise to keep my AdWords Campaign going, honest.