Strange errors in all Open-gl based games

Ok heres my problem:
All my Direct 3d games run just fine… but all the Open-gl based games
(serious sam, quake3, soliders of fortune etc)
have strange errors (see pics):
www.planetquake.com/project2501/temp/fehler1.jpg www.planetquake.com/project2501/temp/fehler2.jpg

My comp:
AMD K6-2 350MHZ (OC 400MHZ)
96MB ram
Via-based chipset motherboard
Diamond TNT2 Viper 770
(with the newest non-leaked detonators 7.something)

But a friend of mine had the same problems with his:
AMD 450 MHZ
128MB RAM
ALI-Chipset based motherboard (!)
Voodoo 3 3000 (!)
With the 4.00-something drivers

Please help me

THANKS