SBS 2003 Network Browsing

I am having a problem at a client site. SBS 2003 Server is installed. 5 Client PCs (WinXPPro). The clients can ping the server (by name and ip address) and use all the server shares but the clients cannot ping each other (by name or ip address) or use shared printers. I’ve ruled out Norton Corporate Edition Client by rebooting a PC with Norton disabled and trying to ping it.

Any help would be appreciated. Thanks in advance.

Paul