When I try to use DGA2, the screen goes black and the PC completely halts!

Description

When I try to use DGA2, the screen goes black and the PC completely halts!
You are probably using a XFree86 server with a very buggy DGA2 implementation, such as 4.0.3 (shipped with Red Hat 7.1 for example). Upgrading to 4.1.0 will probably solve your problem. You can obtain it from ftp://ftp.xfree86.org/pub/XFree86/4.1.0/binaries/ selecting the directory suited to your platform and following the instructions you find in the Install file.