[QUOTE=Prime95;551968]netboot cpu #3 on a different cable: 2.5 hours and going strong[/QUOTE]

Got my hopes up too soon. Still crashing regularly. Time to come up with a new theory while I'm back to netbooting just CPUs #1 and #4.

[QUOTE=Prime95;552044]Got my hopes up too soon. Still crashing regularly.[/QUOTE]

Please forgive me if I'm telling you how to chew gum, but...

tcpdump might be your friend in these kinds of situations.

Before it crashes, can you verify you're able to write to the disk, and that the `sync` command returns okay? I wonder if it's a problem with the NFS file system going away.

Perhaps you can shell in and leave `tail -f /var/log/syslog` running and see what shows up before the system crashes.