du -s causes reboot

[Eugene Lee]

FreeBSD 4.9p7.  I have a new Dell PowerEdge 1750 that is giving me fits.
I have a ~/src directory containing source tarballs that are unpacked.
A "du -s ~/src" locks up my ssh session and causes it machine to reboot.
No entries in /var/log/messages or /var/log/console.info to indicate the
problem.  No core dumps either.  All filesystems (except root) have
softupdates enabled.  Suggestions to troubleshoot this are appreciated.
Rebuilding the kernel now with -g, hope it helps...