Do I need a new graphics card for Portal 2?

I recently bought Portal 2 off of steam. It runs great, but when the game starts all I get is a black screen. I can hear the announcer and WORDS come up. I have watched the beginning played, so I was able to stumble over to the painting and the chapter title popped up after getting up the second time. Because the only thing that's missing is the video I thought it was probably the graphics card. Thanks!