I've got two wrt54gl Linksys routers and they seem to have the same exact problem from comcast, they can't get an IP from Comcast cable. I was having issues two nights ago with cable internet in general and decided to hook up my computer directly to the modem. It didn't work immediately, but it does now. However, I go to hook up my router and it won't grab an IP. I tried with the other router and got the same result. They are at the latest firmware. Any thoughts?
Could be the Comcast modem is holding on to your MAC address. Turn off the modem for a few minutes and then back on with nothing attached. Wait a minute or two and then plug your router in. See if that works.
Ive got Comcast and today I got the same router and I'm having the same problem. I know I have an internet connection because I can hook up my old router and get on to the internet. I tried Yonkers suggestion, but no dice. Any other suggestions would be appreciated.