Airport Extreme + NTL/Virgin Media

I would be most grateful if someone can tell me what I'm doing wrong. I'm a complete novice when it comes to internet settings.

Just got the airport extreme but it can't seem to connect to get me an internet connection. It keeps saying i have no valid IP address. I'm at my wits end. I have a NTL/Virgin Media cable modem.

I've selected it to connect via Ethernet and DHCP. No joy. Phoned NTL to find out DNS server settings, but no joy.

Tried all the possible combinations in the 'connection sharing' box too.

I've now reverted to my old D-Link router which is working fine.

Help!