WIN XP not letting me use the FAX from a server 2003

I have server 2003 with the fax server running. I also have XP pro clients connected to the shared fax printer from that server. I have two win xp sp2 machines that will connect perfectly, but when the fax console comes up on the others it says it can’t get fax server information. What’s the deal? Why does some machines work and others won’t?