XFX Radeon 6950 with Steam

Hey!
I installed the HD6950 kexts/drivers by Netkas posted on this forum a while ago.

I have installed both Halflife 2 Deathmatch and Portal 1 on Steam but whenever I double click them it opens X11 for a split second and then closes. Why is that?

My Hackintosh recognises the Graphics Card and allows me to set any screen resolution I like, I can also play games like Modern Combat Domination and Angry Birds and Asphalt 6 purchased from the Mac App Store.

What is the stage of support currently for the HD6950 Graphics Card? Is there a fix that will allow me to play Steam games on my Hackintosh?

Thanks guys!