Which XFree86 version do you run? You can check it using 'rpm -qa|grep XFree' command from a terminal. In my Mandrake I get this output:
$ rpm -qa|grep XFree
The most important thing - version - is in bold
. For your card, you should be running XFree86 version 4.3. If you have older (with no upgrades in your system after installation, it's nearly certain), you need to upgrade your X.