Using 3rd Party Video Drivers
A number of bugs reported against X in Red Hat bugzilla have been tracked down to 3rd party video drivers. In many cases, however, it isn't immediately apparent that the fault lies with the 3rd party driver because the error occurs while the user is using a Red Hat supplied driver, and not the previously installed 3rd party driver.
Installing 3rd party drivers on your system can cause problems with X, even when they are not selected for use. You should be aware of the issues and potential complications arising from installing 3rd party drivers on your system.
3rd party graphics drivers are generally available directly from the vendor, such as ATI or Nvidia. Some are also available in packaged form. 3rd party graphics drivers that have been sanely packaged specifically for use with Fedora are preferable to tarballs or improperly packaged rpms. Installing 3rd party graphics drivers from tarballs or improperly packaged rpms can cause system instability.
Both ATI and Nvidia's proprietary video driver installation utilities currently (as of ?) replace the Red Hat supplied libGL library with their own libGL. Nvidia's driver additionally installs a replacement libglx.a X server module, removing the Red Hat supplied X.Org module in the process. ATI's driver may or may not replace libglx.a. (if anyone can confirm that, please edit it in).
Once you have either of these drivers installed on your system, you can no longer use DRI with your video card. For example, if you install the ATI fglrx using the ATI installer even if you switch back to the Red Hat supplied radeon driver you will not be able to use DRI. The ATI driver installer has replaced system files needed for proper operation.
If you install Nvidia's driver and later replace your Nvidia card with an ATI card, unless you completely remove the Nvidia driver and restore the replaced system files you will not be able to get Red Hat supplied DRI 3D acceleration to work. You must remove Nvidia's driver completely from your hard disk, and reinstall all xorg-x11 and mesa packages. You can verify that the original files are intact using:
rpm -Va
Installing ATI drivers using the ATI installer, then upgrading your OS version (for example: upgrading from Fedora 9 to Fedora 10), and then using the ATI uninstaller can also cause problems with your system.
ATI's installer makes a backup of the libGL file when it replaces it. When you uninstall the ATI driver on an upgraded system the ATI uninstaller script replaces its version of libGL with the backed up libGL, which belongs to the previous version of the OS.
Again, the solution is to reinstall all xorg-x11 and mesa packages and verify their integrity using rpm -Va.
For more information read Mike A. Harris' email on this issue: http://www.redhat.com/archives/fedora-devel-list/2006-February/msg01178.html