Bryce Lightning Mac (host) Win (client) doesn't work?

[Gwailo]

I'm using 3 computers on my 100 Base-T LAN (behind SMC Barricade):
1) iMac TFT 700MHz 786MB OS X 10.1.4
2) Windows 98 200MHz 64 RAM
3) WindowsXP 2GB Ram 2.2GHz

When I installed Bryce 5 on all 3, I CAN run Bryce on my WindowsXP as a render HOST and Bryce Lightning on Mac OS X as a RENDER CLIENT, but not the other way around. That is, I can not make either of my windows machines work as render clients, but I can make my Mac OS X work as a render client when WindowsXP is the render host.

Is there a known issue with that? Why do you suppose I can connect to my mac as a render client, but not windows as a render client?

I also applied the 5.01 patch to my Mac and my 2.2GHz windoze box, but it didn't change anything.

I'd really like to be able to use my other terminals as render clients when they're not in use locally, which is rather frequent.