Applications cannot use shared Internet Connection

Hi there,
I have a wireless network containing a server pc and a single client. (Both
running Xp Pro SP1). Since last week programs (except for IE and itunes) on
the client machine havent been able to access the shared internet connection.
For example, i recieve errors with outlook, messenger and norton antivirus
saying they are unable to connect. I have 'Black Ice' firewall software
installed on the server machine, with no firewall enabled on the client.
As I have mentioned IE and Itunes can connect fine. Has anyone experienced
similar problems? I thought it could be a problem with the firewall but all
the settings seem alright.

Thanks in advance,
simonstevens35