I just came across some info that this may be a problem with the DHCP 
client in FreeBSD/m0n0wall...

http://www.chetnet.co.uk/portal/forum/archive/index.php/t-2650


CygnusX1 wrote:

> Hi,
>
> Comcast is in the process of taking over my broadband service from 
> Insight Communications.
>
> Since switching to a Comcast address range, I have been having 
> frequent problems with my Internet connection. In the log (the SW 
> error should be irrelavent--they are trying to put motorala firmware 
> in my Linksys modem) below is a typical sequence that repeats over and 
> over while connected via m0n0wall...then, at 15:32, I connected a 
> sacrificial XP machine directly to the cable modem at which point the 
> modem properly synched up immediately. On the XP machine, the network 
> interface had the following values:
> IP            68.x.y.z
> subnet      255.255.252.0
> Gateway  68.x.a.b (within same subnet as IP)
> DHCP      172.30.58.34
> DNS        68.57.q.r
>                68.57.q.r+1
>
> I am guessing that the IP address of the DHCP server is giving me 
> trouble. Any ideas? What else do I need to provide to complete this 
> picture? (There is no route to 172.x.x.x in m0n0wall routing table.)
>
> Same issues using a Linksys BEFCMU10 modem and a Motorala SB5100 modem.
>
> One more question: Is there a way to force m0n0wall to release and 
> renew DHCP on the WAN interface?
>
> Thank you for any help.
>
> Cyg