MSI K7N2-ILSR 3d video problems

Hello ppl,

My config is as followes :

MSI K7N2-ILSR Motherboard
ATI Radeon 9800 Pro
AMD Athlon 3200 CPU
corsair twinbank memory (2 x 512) 400 mhz MEMORY

When I'm using 3d video (screensaver or the ATI demos, the system
freezes.
(Hard reset is the only way to reboot)
if I don't use 3d video the system is stable.

It seems like a directx 9a issue (or direct 3d ?)

Does anyone has the answer ?

Greetz... Richard