XP Home Stopped Sharing - Doesn't Answer Pings

Small workgroup network of XP (sp3) systems. One system has "gone mute". It can ping/browse/access-shares on other systems in the workgroup, but it doesn't respond to pings/browses/share-accesses from the other systems -- INCLUDING ITSELF!

Attempting to access it's own shares via network neighborhood or running "\\computername\sharename" gets the same "...not acccessible. You might not have permission...network path not found" error that the other systems get when trying to access this system.

**UPDATE** ran the Network Setup Wizard, and the system is now able to see/access it's own shares, but still doesn't answer pings or allow access by other systems