I'm still having problems with the back button when using an NTL default proxy and am not sure if I've explained the problem properly?
Below is an example of how Cable Forums looks when I use the back button on an NTL proxy.
http://homepage.ntlworld.com/zendawn69/backformat.jpg
And here is how it should look normally
http://homepage.ntlworld.com/zendawn69/normal.jpg
Hopefully this will help explain the problem better and pinpoint whats causing the trouble.