Do you have a router? It's entirely possible that Netguard is picking up the IP your router is giving you, which would not be an NTL IP.
Note: I have never installed Netguard (with or without a router) so could be wrong, but that seems the most logical explanation.
If that is the problem, then there are good, free, firewalls and Antivirus programs. I use ZoneAlarm (
http://www.zonelabs.com) and Avast Antivirus (
http://www.avast.com).