ME Wireless networking with XP

I asked this back in May, but now can't find the posts (I'm guessing older
posts are deleted). If it's still out there and you can help me find older
posts, "thanks", if it's lost forever, here's the problem:

My friend has an older desktop running ME, and a Notebook running XP Home.
The Desktop is hooked up to internet using an Orinoco PC Card Setup. After
he bought the Notebook he also bought a wireless router and wireless card so
he could share the internet connection. The ME computer is connected to the
wireless router by network cable (to router WLAN port). The internet sharing
works fine, but when we try to play a game over the network the computers
won't see each other. Actually, sometimes the XP machine will see the ME
machine when the ME is being HOST, but when you try to join the game the XP
machine will close the game down. When the XP is trying to be HOST, the ME
machine won't find the game at all. I have a feeling it's a configuration
problem, but I'm not sure where or what to look for.