the task fails every time with the "unable to launch the ghostcast service process"
That's a really unusual error message. Whatever the cause, that error message describes something happening on the console machine itself, either in launching the process or accessing the image. The network configuration shouldn't be involved at this stage of things unless the source image is located on some network storage.
Let me explain how this works:
As part of executing a task, once things get to the imaging stage the console machine network service
ngserver.exe spawns a copy of the interactive GhostCast utility
GhostSrv.Exe to handle the imaging process. When launched this way on behalf of the console, the GhostSrv.exe process connects to NGServer.exe and notifies it of how it is progressing.
Now, if you launch the task on the server, the GhostSrv.exe process is launched under the identity of the user who started the process, and uses their permissions to access the underlying image file (client-initiated tasks launch as the SYSTEM user).
The first thing to check is whether the person launching the task has permission to access the underlying image file; I'm not completely confident that we get the right error message for this in every case. It may be that if an image is stored someplace (e.g. under the "My Documents" folder) with an unusual access-control list it may be that the underlying cause is a permissions problem and this error message is coming up instead of something more friendly.
If that's not the cause of the problem, then it's probably something more exotic. Can you launch the GhostCast process interactively on the console machine?