The newly released Mac mini has revealed a new set of ATI drivers buried within its default Mac OS X installation. New Macs always have a slightly newer version of the system software installed that provides support for the new hardware. In this case, the software also revealed early support for the ATI Radeon 5 series. Some tinkerers have been able to use the software to drive an ATI Radeon 5870 on an actual Mac Pro. Meanwhile, a recent NVIDIA Driver release have shown references to NVIDIA GeForce GTX 400 series support.

don't download the driver from nvidia, they rereleased the drivers, but without the necessary NVDAGF100Hal.kext.