XP not talking to Win98

I just set up a P2P with four PC’s. One machine is XP and the other three are Win98. All three Win98 PC’s can see each other and two of the Win98 PC’s can see the XP. The XP can see those two Win98 PC’s but can’t see the one Win98 PC. When I powered up all four machines this morning none of them can see each other!?!?!?
Please help!!!