Networking issues with MN-500 and Belkin 802.11g access point

Belkin punted this, so I'm turning to a newsgroup.

I have the following setup:
MN-500 (192.168.2.1)
Windows XP Home desktop (Machine A), connected via
ethernet (192.168.2.2)
Windows XP Pro desktop (Machine B), connected via
ethernet (192.168.2.3)
Windows XP Pro laptop (Machine C), connected via WiFi
(192.168.2.4)
Belkin F5D7130 802.11g Access Point (new), connected via
ethernet to the MN-500 (192.168.2.254)

Network is DHCP-assigned, 192.168.2.1/255.255.255.0.
No machines are running Windows XP Firewall

When I connect via the 802.11b WiFi built-in to the MN-
500, I can see all shares on all machines, can use Remote
Desktop, etc. Life is good.

When I connect via the 802.11g card, I can see the
Windows XP Home machine and it's shares. The Windows XP
Pro machines cannot see each other. They can each see
the Windows XP Home machine. Also, Remote Desktop
doesn't work between the Windows XP Pro machines.

Is this enough information for people to start giving me
advice, or do you need more information?

Addendum: I can use Remote Desktop if I address either
machine by its "outside" (DNS-hosted) name.