Please help. I cant open certain websites or use pay for things on the internet

Please help, I am using Vista and have Norton 360.

Certain websites wont open, like Argos, or Adobe, and when I try to buy something on the internet, and get directed to rbs on securesuite to enter my online banking password, that actual page never loads, so I cant buy anything. I habe tried deleted my cache etc, but it wont work. I have turned off both Norton, and Wondows firewall, and also tried Firefox, and Opera, but still nothing.

Can anyone help?

Thanks.