I came accross an interesting problem the other day where a HP 4000N printer was working properly excepted that it would not print multiple copies. It would however print multiple pages. Changing the print driver to HP LaserJet 4, HP LaserJet 4100 PCL 5 or HP LaserJet 4100 PCL 6 did not fix the problem.
The solution was to change the print processor to winprint.
Solution taken from: Only prints one copy.