I've read how several people are having problems with recent releases on
these machines. I have tested the amd64 and i386 ports, 4.1,
4.2-stable, and -current.

i386 seems stable.

amd64, any version, eventually reboots itself. Sometimes right after
fsck (hello reboot-loop), sometimes if you just ssh to the box, or
start a kernel compile, etc. It usually only takes a few seconds of
interaction with the box.

- HOWEVER -

These boxes appear to be rock-solid if you avoid the disks. I have a
few that run diskless -- and they do not fall over, no matter what I
throw at them. 4.2-stable and -current work fine there; the reboots
disappear if my / is on nfs.

If I mount an internal disk and try to use it, the machine reboots.

I'd like to provide more info to the developers for debugging this but
need a bit of guidance... how do you troubleshoot something that
generates no panic and no log entries and the machine resets?

What can I do to facilitate debugging this?

dmesg available at: http://openbsd.rutgers.edu/x4100m2-dmesg.txt

Thanks.