Video Card Problem?

My video card suddenly stopped working. It no longer outputs video. The fan on the graphics card is constantly at max. What could be causing this. It has been working fine. I recently updated drivers. I recently used Vista's sleep mode. those things could have something to do with it. The card is a Radeon HD3850.|||The driver update would be the most obvious answer.....IF they were directly from ATI and you happened to have a card that came with a computer (HP or Dell sometimes ONLY allow their drivers). Sleep mode would not do it.