Unable to get on internet - takes an hour or so

Hi

My first thread here - hope it will stretch you guys.
Problem is connecting to internet sites - can connect straight away to ftp.microsoft.com. Occasionally can get https sites. Never http sites until after an hour or so after letting the automatic helps do their bit and telling me there is no problem. All of a sudden it will open those sites. I can then surf to my hearts content
Running XP connect to a home hub via an ethernet cable.
IP is BT Yahoo (UK)
Browsers - Firefox, IE and BTYahoo - all have the same problem
A mobile BB handset will open internet ok - I assume it will link via the home hub.
I can connect to BroadBand - the BT desktop help confirms as does the BT Broadband help folk in India.
Outlook Express will download emails and attachments ok but not any of the pics which are part of the email itself.
http sites say "waiting for www...." or "website found waiting for reply"
https sites will open but not fully.
Turning off the Norton /Symentec firewall does nothing.

Hope you can help

Johnno K