"(computer) unavailable" on home network
 

I'm trying to put together a home network using a
Microsoft wireless router. All 3 computers are able to
access the Web through the router, but not able to access
one another. I have confirmed that they:

1) all have the same WORKGROUP assigned
2) all have folders designated as "Shared"

Still, when I try to access one computer from another via
MS's Broadband Network Utility, the other computers are
not identified by name (only by IP addresses) and I am
told "computer unavailable" or "no information for device
available."

What other settings have I missed?