BETA3: network processes hang in keglimit (unkillable)

I just experienced a complete loss of network, where every network related 
process would sleep on "keglimit". I was unable to recover from this 
situation. I tried killing the processes with SIGKILL, but it didn't work, 
and I tried to bring the network interface (em) down and up again, which also 
didn't work. A reboot "solved" the problem. The machine was handling some 
major traffic, both TCP and UDP.

Apparently the system was waiting on some resource to free up, but what could 
it be? How can this situation be avoided in the future?

uname: 8.0-BETA3 FreeBSD 8.0-BETA3 #1: Sun Aug 30 01:23:36 CEST 2009 amd64

-- 
Pieter de Goeje