So, I seem to have the same problem Ignatios reported a few days ago;
_both_ of my Sharks hang hard (no response to any DDB commands) some
random amount of time after boot (on the order of 5-15 minutes, but
once I had it happen during a fsck while booting).

A little more digging seems to have uncovered the culprit; I finally
figured out this didn't happen on the SHARK kernel, but it happened
on my custom kernel.  It seems that the NTP option (the kernel
phase/frequency locked loop) causes a random hang, _even_ if you're
not running xntpd.

Ignatios, do you have "options NTP" in your custom kernels?

I'll try to figure out exactly what's going on, but I thought
everyone else would like to know.

--Ken