I upgraded from FC4 to FC5 on my d600 and lost Direct Rendering. On FC4 I'd been using the ATI proprietary driver (it helped smooth googleearth scrolling). I was not particularly attached to using fglrx, but I hated having no 3D capability - watching videos became jerky etc.
I removed the fglrx package and re-installed all of the xorg-x11-* and mesa-* files from the FC5 DVD, but still glxinfo reported direct rendering as no.
The problem is the ATI proprietary driver leaves broken symlinks lying around that the X server tries to use. Since the links are pointing into the void, DRI fails.
I removed these two dead symlinks:
and restarted X.
Viola! The native FC5 Radeon driver now provides direct rendering! I'm a happy camper again.