I was messing around with AGP Aperture size in my BIOS for completely unrelated matters, and upped its size from 64mb (the default for my chipset) to 256mb. Nothing much happened but I decided to leave it on 256mb anyway.
I launched Guild Wars, and after about three hours of play, I had my first crash ever. The game simply froze up along with the rest of Windows, all the while making a high-pitched noise through my headphones.
Needless to say I reverted to my old AGP Aperture size of 64mb. Been playing for five hours now and no crashes yet.
My system specs for the record:
P4 3.2ghz
Asus P4C800 mobo
2GB Corsair DDR
ATI X800 Pro
Creative SB Audigy 2
Freezing due to AGP Aperture size [FIXED]
Lagg