Firstly forgive lack of error message detail.  I am at home and my problem is at school.  Also no ghost expert, never have had to be because it always works perfectly!
I have been using ghost solution suite at school for around five years now.
I create the image store it on the server and then multicast usually to 10 or more computers at a time up to 24.
I use a UBCD in fact I have two and do them two at a time so its not as though its specific to one UBCD.  
I use TCP/IP connection map the pathway to image to ghost.exe etc. same as always.  
Insert administrator password, domain name etc.  
Latest run I did 18 workstations at once with one image, then 25 with a different image.  Both worked beautifully as usual.
This last time I did a small run of 4 with the same image, same method etc. all as usual.
The server accepts the clients, the multicast process starts, then about half way through the process it hangs, messages vary from connection dropped, connection lost, cannot find place to store image, something about A: drive though I cannot remember exactly what.
I set the session to accept ex number of clients - works great.  
We run McAfee at school.  I disable while I multicast. Its never been an issue.
The network connections, switches etc. are all the same as they have been for years - and have been working fine.
Not only did the multicast freeze but it had got part way through wiping the hard drive on the client workstations so now they are dud as stand alone workstations.
Very annoying.  
Also don't have enough hours at school to spend lots of time on trouble shooting - hence doing it at home.
So to summarise the client is making the connection to the server and accepting the image then its freezing half way through. 
Any advice would be gratefully received - I want to get this new classroom up and running asap!