You must change your articles and increase the quality of articles. after that take quality pr3-4 theme related links.
it's just google dance, keep build more links to your site and provide good content you'll back in 1-2 months
Your site might be affected by the change in Algorithm of Google. If you have already change the content of your site, it will take some time before you see the exact result of the change that you make on your site. Just wait a couple of weeks more. Im sure something will happen.