Found it!

In case you’re wondering why this server was off the network from time to time, well, the poor thing was crashing. On a regular basis. Like a religion.

I made all the upgrades, I tried some tips from friends, but it kept crashing.

But now I know. Bad memory.

Well, I’ve removed the bad memory (at least I hope I did remove the right one…) so it should be more stable now.

BTW, memtest86 is available directly from any Fedora boot CD. Just type memtest86 at the prompt.