I have several HP 4100 (and some other models that have the same problem) that seem to stall when trying to print. The display goes from ready to processing data and back to ready...over and over. If you cancel the job at the printer, or cut it off and back on again, it starts printing one line of printer code on every sheet of paper in the tray until it is empty. What can i do to trouble shoot this problem, or has anyone else seen this before?