[exim] exim and clam going nuts

I'm running FreeBSD 5.4-RELEASE, exim 4.62 and clam 0.88.2 on a P4 2.8
with a gig of ram.

What started happening today is clam would suddenly start using 50% of
the processor. Doing a /usr/local/etc/rc.d/clamav-clamd.sh stop sits
and waits for the PID of clam to stop. When I did a kill -9 of clam's
PID, the machine went completely bananas and very unresponsive:
# w

6:08PM up 4:49, 3 users, load averages: 605.85, 749.77, 573.68

On killing exim by doing /usr/local/etc/rc.d/exim.sh stop then killall
-9 exim-4.62-0 restores the machine to normal.

I started exim and clam again, and after a couple of hours, the same
thing happened. I can't find anything in either exim logs or clam logs
slightly out of the ordinary.

This machine has been running with no hickups for months. Has anyone
else had even vaguely similar problems?

-John