Well I got it working after taking the advice thanks a lot.
Despite cycling through everything I think it was the resetting of the Comcast MODEM completely via the reset button that did the trick. The IP address changed as per previous instructions.
I have to say though I am very...
I just upgraded from a Belkin G router which was connected to my comcast router which worked perfectly but I needed more range and a speed boost for upstairs so I bought the N router from Apple. I added an airport extreme and I can't get out to the internet.
The wireless network is set up fine...