Linux just happens to work again!
The update from Ubuntu 7.10 to 8.04 was a trainwreck. Bugs on all sides. Mostly audio and video-driver related. They were all reported and worked on, so no fault of my own. Then I went to PCLOS for a month or two until it went belly-up. So back to my old cutting edge friend Fedora which started to hang for no apparent reason, so I try to go back to Ubuntu 7.10, but now I have the same problem as on Fedora... I just get those strange lockups where I can move the mouse, and the programs seem to keep working fine, but I can't click anything. So I try good old Suse, my first love, which behaves like a monkey on crack right after the install, and I'm positive this is one of those crackpot hardware errors that are impossible to troubleshoot (cpuburn, memtest... all return nothing... tried a different harddrive... same problem).
So I was using windows for the past months that I installed earlier this year for a LAN-party. It's an ugly son of a bitch, but for some reason it works on this hardware and it served my basic computing needs.
A couple of days ago I started booting into CentOS again, and behold! No crashes so far!
I think it mysteriously solved itself.
I'll keep my fingers crossed.