Users of NVIDIA's Quadro 4000 workstation graphics card may have a problem with 3D acceleration when updating to OS X 10.6.7. Apparently NVIDIA's display driver was incompatible with OS X 10.6.7, and during the installation process, the updater simply removes it. Without having the right driver the system can't take advantage of all the Quadro's features, and you may end up wondering why some things aren't working.
The good news is that there's an easy fix. Earlier today NVIDIA released a new version of the driver, and you're a quick update away from having everything running normally again.