Another thought:
1 Look in the Printers Folder and check the properties of your printers. Make sure, under Ports, that the printer is linked to the proper port. For example, I hook up the LaserJet 5P with a USB to parallel cable, and under Ports, it shows a check mark beside USB001 Virtual Printer port for USB HP LaserJet5.
2. In the Printers Folder, look in File -> Server Properties -> Ports, then Drivers, and make sure you have no superfluous and competing drivers. If you uninstall all your printers, you can see if any drivers are left over and remove them. This will force a complete install when you start up.
.... T