WinXP network w. TCP/IP & IPX/SPX

I have a home network with 3 computers. 2 of them have WinXP Pro and the 3rd
WinXP Home. They are connected through a switch and my XP Pro computer is
sharing an Internet connection with the others through an extra nic. All this
works great, no problems. When i wanted to play a game with my kids that uses
IPX, we installed IPX/SPX on all of them. The problem is that the other two
computers can connect and play, but i can not join. And when i try to host a
game, they can't find me. We have configured the properties for the IPX
protocol the same way. I assume that it has something to do with my computer
having 2 nics and perhaps the shared Internet connection. Any help?