Multicast and different versions of VLC

[Mattcrl]

I'm having some difficulties with multicast and different versions of VLC.

I have a wireless mesh network (with a couple of identical nodes) which supports multicast and four different computers each connected (wired) to a node in the network. I then multicast a CBR video stream from the four computers, one by one, but not all directions work.

1. VLC 0.8.6e - Windows XP
2. VLC 0.8.6e - Ubuntu 9.04
3. VLC 0.9.4 - Ubuntu 8.10
4. VLC 0.8.6e - Ubuntu 8.10

This works:
1 -> 2 (streaming from computer 1 to computer 2 works fine)
2 -> 3
4 -> 2

Doesn't work:
2 -> 1 (streaming from computer 2 to computer 1 doesn't work)
3 -> 2
2 -> 4

Which node a computer is connected to doesn't matter, same outcome whatever setup I've tried.

Is there a simple explanation why not all versions of VLC works when streaming multicast?