Data switch transfer

Help, :sad: we have a xerox m15/m15i printer/fax machine. It is connected to our 2 brand new Dell computers with Windows XP. When ever we switch from printing to either computer A or computer B our computer will start printing multiple pages of wing dings, weird fonts etc. We have tried the following. moved the printer so it is on a shorter parralell port cable, installed and reinstalled the software. Changed the printer ports from C to D (they were orginally A & B). Nothing seems to help.

Any suggestions. By the the way the people at Xerox Canada recommend that we try this but nothing seems to help.