Xerox WC PE120i not printing labels

Hi folks,

we have a xerox workcentre pe120i printer connected through network to our LAN at the office, and although we can print through the network normally, when we try to print labels from the PC next to the printer, it doesn't print. It queues it to the printer, and "completes" them there on the PC, but nothing arrives at the printer itself! Once or twice we have succeeded, at the beginning, now we cannot print them no matter what we try. We have also tried to save the "mail-merged" labels as a file at the final stage of the mail-merge, and to print some or all of the saved pages as labels or as normal A4, but same problem occurs.. What do we do wrong??
any help appreciated