I have a Netgear WGR614 and the setup wizard did not detect the correct connection type for NTL: it was detected as a static IP/DNS type connection as opposed to DHCP assigned. I'm wondering if this is causing your problems.
What you need to do is browse to:
http://www.routerlogin.net/basicsetting.htm and login as admin/password
Make sure that your Internet IP Address is set to "Get Dynamically from ISP"
And Domain Name Server (DNS) Address is set to "Get Automatically from ISP"
hth