I have two 1.6GHz G5 Power Macs that I use to host my company's web and email. One machine is a backup on the DNS incase the first goes down. Well, I noticed the backup machine would freeze up on me fairly regularly when I was working on it directly. The computer would freeze and would then reboot itself after 150 seconds. I had a hard time duplicating the problem for a while until I tried to untar a moderate sized file. It would freeze every time but at different points in the process. I know the file is good because the first machine has no problem with it. I can not find the original restore disks that came with the machines so I haven't been able to run an Apple Hardware Test. I have swapped the hard drives, memory, graphics card, and fans between the two machine and the second machine still freezes while untarring as well as doing other menial tasks. I tried a different hard drive with 10.3.5 instead of OS X Server on it and it too would freeze up on me. I do find a few things a bit odd, however. The first is that I can SSH into the bad machine and untar the file everytime with no problem whatsoever. I tried untarring and rm'ing the resulting folder at least a dozen times in a row over SSH all with no problem or freezing. Second, I am able to run Altivec Fractal (maxes out the CPU and Memory) for long periods of time on the machine with no problems. Finally, the temperatures between the two machines seem to be pretty close. My suspicion is that the logic board is dying but why would I be able to do the do something over SSH that I couldn't do at the machine. Any ideas?