Is your MBP still under warranty? Apple Care? If it is, you might want to give Apple support a call and make an appointment with them to take the machine on in and have them look at it.

From your description of the problem, it sounds like the video chipset in your machine may have failed. Since that is not a user serviceable part (it's surface mounted on the main board) an authorized tech will be needed to make the repair.

Regards.