When DNS over DHCP breaks?

[dmorin at morinfamily.com (Duane Morin)]

This morning one of my machines, which is connected via DHCP to my router, 
apparently stopped doing DNS properly.  I am guessing this because all of 
the operations from that machine that connect directly to an IP, i.e. my 
mail program, work fine, but attempt to go to a web site by name fails.

My statically configured box which has /etc/resolv.conf with 3 nameservers 
in it continues to work fine (although I have not rebooted it 
lately).  Anybody got suggestions on what might be going wrong with this 
machine, and where I can start looking?  I tried telling it the DNS servers 
(while keeping it on DHCP) but that failed.

Ok, wait, tried a few things and it's weirder than I thought.  Any attempt 
to ping addresses by number outside of my own domain fail as well, which 
suggests I don't have a connection to the outside.  I do have a connection 
to the inside of my network, though, so I know that I have wireless at 
least.  So I guess what's happening is that my router has decided to stop 
allowing this machine to connect to the outside world?  Why would that 
be?  I have confirmed that my other machine can connect to outside machines 
both by name and number, and look things up in dns.

This is an XP machine, in case that matters.  The static box that's working 
is Linux (of course).

Duane