You won't be able to change your IP with ntl so doing ipconfig /renew makes no difference.
Turn your cable modem of for 2 minutes and reboot computer, switch cable modem on leave for 2 minutes - just try the basics ...
Try changing proxy which can be found at the bottom of this page
http://homepage.ntlworld.com/robin.d...trancache.html highlited in green not blue.
if not check the ntl status page on ntlworld.com to see if there is a national or local fault, could not be reported so leave for a few hours, if still not fixed give them a call.