try AGP 2x in bios
I have been trying for months to get the problem of freezing randomly sorted out.
On my system the problem appears to be that the voltages to the motherboard are too low (the power supply does not appear to be totally adequate) which results in the graphics card not being able to run at full power. When I dropped the AGP to 2x in the bios the problem seems to have gone away at least no hangs for the last 4 h when it was hanging every 2 to 10 min). Interestingly switching the AGP off in the config file didn't work. This could be because SUSE has it compiled in and I was too lazy to recompile (my system would require several other non-linux-kernel modules to be recompiled as well).