What Bobo says. Don't even know if you're still around after all this time OTazman, but just in case:

1. Reinstall - ensure your're not using a hardware accelerated Xfree86 (you can always change it later) - and see if that helps.
2. LinuxNewbie.org is a great resource, also, check out Mandrake User Board at http://www.club-nihil.net/mub/ - there is tons of information there on problems of this nature, most of which is useful no matter which distribution you use.