Network Problem

i have a windows nt 4.0 server and connected with an 10 mbps hub and switch of IBM . The server is connected to 60 clients in the same buliding . we have XEROX 432 t Network printer , scanner and fax machine in that . what is my problem now is the network printer is connected to every one . some the network printer goes offline (ie the printer is in on mode but the clients can not give any print to the printer . he has shutdown his system and then restart then the printer comes to online mode . what would be the problem . is it problem with server , client or the xerox printer . so pls help me out with problem .