I run Debian Lenny 64-bit on an HP server with an Intel Core 2 Duo processor. It boots with LILO rather than GRUB because it has an XFS root partition. Up until today it had 3 GB (2x 512MB and 2x 1GB) of ECC RAM. I have been getting ECC errors from EDAC occasionally on a single slot but since I had no crashes I wasn't too worried.
Today I tried to do a Seagate firmware update which Seagate recommended for two of the drives (data only, not /) which are in a RAID-1 in mdadm on that machine. I didn't manage to do this, or even get to the README for that disc as the it was taking forever to boot. I got fed up and tried to reboot the system. It hung after three lines of ...s from LILO.
I thought that I probably had some bad RAM due to the ECC errors, so I tried many different configurations (with 6 DIMMs, the four mentioned plus 2 non-ECC DIMMs, obviously not at the same time) but couldn't get it to boot.
I ran memtest86, hoping to isolate the bad RAM. This resulted in the exact same error every time in Test #2 of memtest86, no matter which DIMM I used and no matter which slot. It always returned 3 errors on the first occupied RAM slot. I cannot make sense of the errors it returned but can produce them here if it's relevant.
Attempting to boot Debian off the main disk after this did not even show the word "LILO". It just hangs with a blinking cursor. This, together with the fact that there were memory errors every time, caused me to believe there was something wrong with the motherboard or with the CPU.
However, very oddly, Knoppix boots up happily and runs with no problems. I cannot run lilo because Knoppix is 32-bit and the system is 64-bit. But this makes me question some of the above stuff -- surely Knoppix can't run with RAM errors or a bad processor?