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.