My boxes are all running Linux. I don't have a single Windows box booted. I really do not believe it's an instability in the machines. The systems were still running, and appeared to be stable when I found them. I've run other software for weeks on end with these machines, and have never experienced this sort of problem.
Dang. Sunspots? Yeah, sunspots is my second guess.
Interesting. Same error with this Linux box:
http://forums.2cpu.com/showthread.php?s=13ebca518e715bf508d2b6e097af3b1a&threadid=60503
There were others on a Google search but that's the first I came across. File system?