I found why the server vick0 was crashing. It wasn't the motherboard, or the memory, or the CPU, or the power supply.
One of the tasks of vick0, is to run a large (3tb) hard drive for backups. And each time I swapped anything out, I kept that large drive connected. Because an attached drive can't possibly be causing crashes.
But it was.
Now I've swapped out that hard drive, and it's sitting on the desk in front of me while I load up the replacement drive.