Workstation fails to join session on HP dx2400

I have a bunch of new HP dx2400 PC's with a weird problem.
I can manually take an image of the PC without issue.
I can manually restore an image to the PC without issue.
However, if I setup a multicasting session I have a failure.

I setup a manual multicasting session at the server.
I go to the PC and start an imaging session.
IMG SESSION TEST at the bash prompt.

Imaging starts and displays "Listening for session master", and never
joins the session, or displays any errors.

I can go to a non dx2400 pc, use the same command, and it instantly
joins the session. I have plugged the non dx2400 pc into the same
network connection as the problem dx2400, and again that pc joins
instantly.

I've also use the current boot cd with the same results.

So it clearly has something to do with the PC.

Anyone have any ideas of where to go next.

This is Zen7 and updated to the recent patches
ZDM7SP1_IR3a
+ ZDMIR3a_Imaging_SLES10SP2
on NW 6.5sp6