Unfortunately, the ATI 3.7.6 driver for XFree86 4.3.0 is not compatible with XFree86 4.4.0. We will all have to wait until ATI gets a new driver out that supports XFree86 4.4.0. In the meantime though, you can use the generic radeon driver that comes with XFree86 4.4.0. It is not quite up to hard core gaming standards, but will give you <cough> decent enough 3D/OpenGL support while you wait.
Just edit your XF86Config file and add/change the following:
Option "AGPMode" "(1, 2, or 4)" ;(8x is not yet supported
Don't forget to uninstall/delete your XF86Config-4 file, ATI 3.x.x driver, and rem-out your modprobe fglrx first.
Hope this helps someone