Hurray! I finally got the brightness buttons working on my laptop. Ever since I got the laptop the brightness buttons would work fine until I started X, then they wouldn't work again. Was poking around and looking at the laptop market tonight and found a page that mentioned that they had the same problem and they fixed it by adding:

To their X Device section. I'm not sure this card is even a 4x agp card, but adding that in there seems to fix the birightness button pretty handily.