networking won't come back up until reboot after ISP outage

[umage]

Hello. I have had 3 network outages this week, and everytime it 
happened, I found that my freebsd8rc1 machine/router was unable to 
communicate over the WAN interface even after the outages ended. A 
reboot helps, but that's not an acceptable solution.

The symptoms are very weird: even though dhclient successfully receives 
a dhcp lease and sets up the interface, I am unable to ping the gateway. 
The ifconfig utility says the interface is up and configured correctly; 
netstat -arn says routes are set up as they should be; and tcpdump 
reports random network traffic arriving on the interface (so the network 
itself is up and running). Taking the interface down and back up doesn't 
help, reloading ipfw rules doesn't help.

I have some more things to test - whether tcpdump reports any attempts 
at outgoing traffic, and whether disconnecting/reconnecting the network 
cable will do anything. And maybe reverting ipfw rules to what I've been 
using before. Other than this, I have no idea what else to do...