Originally Posted by NoWhErE

I'd say its your backlink profile. 99% do follow links with 2/3 of them being sent to your homepage with a sudden velocity increase that starts in september to october. That's an unatural increase. You should have asked your link supplier to spread it out over time instead.

I'd say you got a minor slap from the big G.

Note: Your home page is somehow coded differently than your other pages. Try cleaning up the template (might not be why your page isnt ranking, but it bothers the hell out of me)