This is unlikley to be anytihg to do with the ntl STB or connection to it if you cannot see the wireless network.
You can confirm the ntl connection is working OK on the router by going wired from a LAN port on the router to your PC. That should show you have internet connectivity. As you are using a STB, your router needs to be registered with the ntl servers. Assuming you have done the power off and on bit on the STB and router and PC when first connecting the wires, you should get taken straight to the registration page when you first go on the internet. If not try entering "start.ntl" in the web browser address book.
http://homepage.ntlworld.com/robin.d.../register.html
Once you have a wired setup Ok, you can check the router's wireless setups, and hopefully reconnect usign wireless. Remember to disconnnect the wired connection from your PC
If you continue to have isues with wireless, check you have current drivers, wireless is enabled, try disabling firewalls and antivirus.