TCP/IP Gets Internet-not LAN

Have a problem where Windows XP Pro does not “see” another System with XP Home or Win ME, yet IE will browse the Internet just fine. In fact, all my other systems will browse and see each other also, but the Heome Edition won’t access anyone else on the network. I’ve also got a customer with a similar problem: XP pro and ME will both allow IE to browse, but they don’t see each other on the network. Have removed and reinstalled ME’s TCP/IP protocol and related drivers, with no success! I’m going crazy!