Problem getting Multicasting to work

Environment

Single Tree
eDirectory 8.8.2
Netware 6.5 SP 7
ZENworks 7.01 Ir3
Clustering 3 x Nodes

We have ZEN imaging working, and all seems good, I can PXE, pickup the
correct image based on IP Address.

Now we are trying to get Multicasting working. Using an Image on the
Netware server

I have seen a few people have had this issue or similar.

Testing so far I put the Server and Workstation on the same switch. As
the Comms guys told me Multicasting had been enabled, but I wanted to
check..

The workstation gets an IP and then goes into Imaging.
The workstation finds the Multicast session and becomes Multicast
client. Then displays the message

"waiting for session master to start"

I changed the settings to only 1.

I checked that the SERVER-ZIS has root access.

I Then tried to do a manual multicast and exactly the same happens, it
finds the session but then displays the same message "waiting for
session master to start"

Just wondering if anyone has any tips? or advice?

Thanks

Pete