There was a Panda data refresh on 19th April, 2012. You also need to check if your website was penalised by the very latest ‘Over optimization’ penalty or the even latest ‘Penguin update’.
http://searchengineland.com/the-peng...al-name-119623
Here’s Matt Cutts helping you with other possible reasons:
http://www.youtube.com/watch?feature...&v=gx04qNrCbnk
Techniques to follow now?
Avoid indulgence in keyword stuffing, link spamming & linking the same anchor text to multiple sources. Include unique, informative content in your website and make the most of social media interactions.