Any X1900 users have spontaneous reboots?

Question

All:
I do realize that this may not be directly related to Motion, but it could be related to the graphics card, and this is the largest group that I can think of that would have X1900's.
I've, in the past, experienced a hard reboot during Motion renders when the X1900 intake was dirty. It seems that throwing a kernel panic is pretty normal if the X1900 doesn't have clean airflow. So, I clean the intake ever few months or if it gets loud.
Recently I've had my system (Mac Pro) reboot spontaneously during normal non-motion tasks like editing in FCP, watching Flash videos in Safari, and lately not doing anything at all (not even touching the system).
I'm curious if anyone has heard anything about this type of behavior based on the X1900. I've searched the webs and it looks like there are folks that have experienced these spontaneous reboots on Mac Pros but there is no apparent commonality. I'm currently cleaning my os drive (as it came back with errors), and have reset the SMC, but I realize this could also be a PSU issue, or even bad memory...
The reason I'm locked in on the GPU is that I know it has, and can bring my system down.
Just a shot in the dark in case anyone here had read or heard about this type of behavior.
Thanks.

Answer 1

Frustrating day but here's something worth reading in regards to GPU's, overheating, and geniuses:
My system spontaneously rebooted about 6 times today while doing all sorts of different things. FCP, Motion, simple web video surfing, and scrolling through a Safari window.
I called the Apple store here in Austin and they said they had the ATI 4870 in stock, but I'd have to bring my tower in because they have to install it. They can't support it if they don't install it. F-it, so I took it in to resolve the issue.
I went to the genius bar and the guy tried to recreate the reboots, albeit unsuccessfully. I think this is because there wasn't enough time to heat the thing up again, and we had a small monitor plugged into it.... and he opened up the side which certainly kept it from overheating. Dhrr. He ran a full system diagnostic and it came back clean. I explained my reasoning, that the X1900 had rebooted my system before, when it overheated. It seemed to be doing that now but without the dust buildup. Maybe old, or something... (or simple HEAT : meaning that heat seems to be the culprit for these reboots from the X1900 whether preceded by fan noise or not).
Then he informed me that the like for like replacement in my 2007 mac pro (no longer covered under any sort of warranty or applecare) was the nvidia 8800, about $600 bucks. I told him I wanted the 4870 that everyone says works in the 2007 Mac Pro, though it's not "supported," for $349. He looked at me funny, went and talked to his manager, then came back and said they wouldn't sell it to me since it wasn't supported on a mac pro 2007. Mind you the 8800 is twice as much, and they didn't even have it in stock.
Then he said they could keep it for 24 hours and try to recreate the problem, for 80 bucks. That way we could figure out if it was the graphics card. After I explained to him that I've scoured these discussion groups for the right solution for what I'm doing: MOTION, and that I'd gotten feedback that the 4870 seemed to be the right solution at the right cost, he told me I could go to frye's or newegg and buy one.
Long story short, it wasn't the best experience. But I did come home and try one more thing. I opted to download SMCfanControl 2.2.2 to actually speed up my internal fans. Basically I doubled the speed from a minimum of 500 rpm to around 1000, resting speed. Still a quiet speed this brought the temperature of my case down about 50 degrees, to an operating temp of about 100F. Before that it was running over 150F. It's been running solid for a WHILE now (fingers crossed). I pushed it with all sorts of stuff and it hasn't rebooted yet.
So, I think a few things are worth asking.
1: Did the System Management Control (SMC) change recently in a system update? I'm wondering if it's not picking up on the x1900's effect on the running temperature and letting it overheat my system.
2: Why can't they staff the the genius bar with geniuses.
3: Germany or the Netherlands?