Cannot access yahoo mail and messenger from client computers

Hi all,

I am using cable modem connected through USB to the server, and the server is connected through hub to the 5 other client computers.

I can access mail and messenger from the server, but not from the client (other website n yahoo services can be accessed from the client). but only the server that can connect to yahoo mail and messenger.

I am using winroute as router (with DHCP server) and zonealarm as firewall.
Can you tell me what might have caused the problems ?

Thank you
Rio