I can see the XP machine in the map, and it is in the correct place. If I hover over the computer icon, I can see the XP computer name, IPv4 address and MAC address, however the icon is not clickable. By not clickable, I mean that the cursor doesn't change shape when I am over it, and nothing happens when I click in any fashion. (Right, left, single or double.) The Vista machine itself and the router are both clickable in the map, and the switch and the XP machine are not clickable.
As before, entering \\computername (where computername is the name of my xp computer) in the "start search" box works, and the explorer window that is launched by that command has all my XP shared directories. File sharing works fine in that one explorer window.