I'm running Ubuntu 6.06 i386 (kernel 2.6.15-23-386) with KDE 3.5.2 and I'm getting funny things happening to my display:

Piccy

Hardware is:
CPU: Athlon 64 3700
Motherboard: Asus A8N32 SLi Deluxe
Graphics: nVidia 6800
2Gb RAM
Onboard sound.
2x IDE optical drives
2x SATA hard drives

dmesg output is here
lspci output is here

What'll generally happen is the dashes appear on the screen, usually near the top, and slowly increace in number, until the box freezes. Once it's frozen, i can move the mouse cursor, but do nothing with it, no keyboard shortcuts work, either.

I'm presuming it's something overheating, given that it happens less when i've got the case open with a desk fan blowing into it than when I don't. But it still happens with the desk fan, and sometimes doen't happen when it's not there.

Any ideas how to fix this?

Can you clean your fans/heatsinks? I make it a practice to give my computer a good cleaning about every 2 months.

I only put it all together 3 or 4 weeks ago.

I'm almost certain it's the GPU overheating.

When it does crash, the computer's not frozen, it's just that the graphics card can't keep up. I've made it recover from the errors a few times with careful applications of fans, which has convinced me that it's a temperature issue. Also, these past few days it's been colder, and i've had fewer graphics problems.

The problem, however, is that i've never seen it report a GPU core temperature higher than 55C, and it's set to give warnings over 100C, but hasn't given any.