Chris Guirl, the owner of the VDrift open-source racing game, has passed along that the problems I experienced
yesterday have been encountered sporadically by VDrift developers. However, those issues had also popped up on NVIDIA cards as well. At this time they do not yet know a fix, but they are continuing to work on the issue. The issue is a VDrift problem, and is NOT specific to ATI fglrx usage.