Your page or site may be over-optimized in Google's eyes, so it's rated more as web spam. Look at the competition pages that are ranking high, analyze their onpage strength and backlink profile. As somebody posted on another thread, if your page deviates too far from the top competition's on certain details (usual example, way too many blog comments or Web 2.0 links), your page could be viewed as the one trying to game the search engines.