just as a possible cause:  wasn't there a bug i the network code
recently found where `ping' would increase the number of used
mbuf's (as reported by netstat -m), eventually running out of
mbuf's ?

this was a couple of months or so and was fixed then, so it
really is only applicable if you're not upto date (in which case
you should have mailed netbsd-bugs, right?  :-)

.mrg.