It's something wrong the authentication mechanism. I've added ntlworld and broadbandplus to the Trusted Zone in IE, removed all cookies, rebooting PC and modem, disabled my firewall and it still doesn't work

Just a blank screen. I watched it once after registering, now nothing. Interestingly, if I go back to the signup page where I entered my name/email address, it doesn't give me that option - just gives me a link to buy broadband

Presumably the web servers think I'm not on broadband. Cheap programmers - get what you pay for.