I had the same problem with my MacBook Pro. It is fairly common. You Tube it, there are plenty of videos. Mine started for 2 seconds and shutdown. An apparent mother board issue. If it is still under warranty send it in. If not, you have nothing to lose, so try this. I did this today and my MBP is now working like new again.
http://russell.heistuman.com/2010/04/27/cooking-the-books-or-baking-my-macbook-pro-logic-board/
There are also plenty of videos on youtube that show exactly how it is done. It sounds kind of scary, but mine was no longer under warranty and I really had nothing to lose. One problem I did have is that I didn't seat the RAM back in properly after I put everything back together, so there was about a half an hour after I did this, that I didn't think it worked, but it did.
It's kind of amazing, but makes sense if you think about what it is actually doing. softening the solder to close up the broken connections.
Good Luck!