Why would I stop ranking for my main keyword?

Ok, so I'm a bit lost here. I have a fairly new website, usually I have no problem ranking any website in the top 3 results in the first page but this one website I recently stopped appearing all together for my main keyword which I find to be SO BIZARRE!, my site is not sandboxed since it's still indexed and ranking for other keywords but the main one just totally disappeared this week, what in the world?

Any advice from y'all?

Thank you.

It happens and on top of that Panda update happened this week. So that could also be the reason?

Umm maybe, I am baffled!, anyone else??

If it was recent, it was probably Google updates. Either that or it is just jumping around a bit.

My site got hit this month too all big keyword lost ranking. I hope they bounce back soon.

Sounds like a Google update. Consider the google disavowal tool if this is a brand new site. Otherwise maybe just scrap it and move on...

Got it figured out with @acotut's help. Ha, all my main kw backlinks died somehow. Witchcraft!