invalid image (Bad Image Signature)

ENV:
ZfD 6.5 SP2
Netware 6.0 SP5

When I try to setup a manual multicast from a master station, I get the
following error after about 50 seconds on each client:

invalid image (bad image signature). I can manually retrieve an image from
the server with no problem. Anyone had this same issue and solved the
problem?

Darrell