Folks asked for an update on this, so here it is. Original problem - Black screen on startup or reboot occurred about 25% of the time, right after the grub menu. No hard drive activity, no boot, no ssh. This problem has existed since I built the computer a year ago. Newer problem - Hard lockups, especially when the load was heavy. I first noticed this when I installed Gutsy on a spare partition. It also happened a few times in Etch, but I was using a custom realtime kernel when it happened. There were also a couple of spontaneous reboots. Hardware - ASUS M2V motherboard, Ath. X2 3800, Kingston RAM, Enermax PSU, some kind of GeForce 6200 with a fan that started getting noisy, Seagate drive, all about a year old. What I did - Replaced the vid card with a slightly older GeForce, and since then, the black screen has only occurred once or twice out of scores of reboots. Got a power supply tester, and the 5V rail read 5.4V one of the times I tested it. Contacted Enermax, and they told me to try a different power supply before I RMA'd mine. Got off the realtime kernel and went back to the stock Etch kernel. No more lockups in debian. Flashed the motherboard with the newest bios after reading that others were having lockup problems with this board. It didn't help. Got a new 350W SilverStone and put it in. Still getting lockups in Gutsy. I believe that the spontaneous reboots are a result of the relative placement of the power button and the wheeled leg of my office chair. I moved the computer back a few inches after I saw the two of them meet once. (Note for the interested builder - buttons on Coolermaster case stick out and require only a light touch. I just built a computer for a friend, and the buttons on the Antec case are recessed and not so easy to press in.) Put the Enermax back in, and everything seems to be fine as long as I stay away from Gutsy and the power button. Thanks again to everyone for their help. Greg