can only access secure sites

Hello, a friend is having a problem since a few days. He can only access his banking site (https) but cannot access any other sites. Windows mail works. He can access the internet through another computer that uses xp, but I'm not sure if the problem is related to Vista. I tried several things but without succes : disabling the firewal, disabling Norton antivirus, installing Firefox

Does anyone had the same problem recently and resolved it ? Does someone have any suggestions ?

Thanks in advance.