Looks like I\'m in trouble.
Even though the video, mouse and keyboard lock up entirely, things are still going on (I can see from my XP box that the server is still running -- though I can\'t connect to it at the moment due to an apparent version incompatibility -- and I\'ve discovered that I can ssh to the machine so I can at least reboot it properly).
I managed to teleport to the new Death Realm and run all the way through it, without a lockup. Took the exit, respawned back in the NPC room, and bam! Locked up after about five seconds. Of course, I can\'t teleport on the official server, but I killed myself, ran through the DR there just fine, spawned back in hydlaa_plaza, rotated left about five degrees... and locked up.
I suspect the problem may be my video card (Radeon 7200). I\'ll go buy a cheap NVidia card and see if that fixes it. But I wonder why I\'ve got no problem in the Death Realm; it just doesn\'t make sense.
Edit: One minor weirdness -- if I\'m running psclient in a window rather than fullscreen, and the cursor is outside the window when it locks up, I can move the cursor all around the screen, though clicking on other windows has no effect. Weird.