Disappearing Printer

I’ve had several machines lose their network printer icon in mid session. It’s as if the printer has been deleted. It doesn’t show in the printers folder and applications can’t find it. It only comes back when the computer is rebooted. It’s happened only on Windows 95 and 98 machines, with different makes and models and different print devices. I’ve ruled out a broken network connection, because the printer should in theory be automatically switched offline. Reinstalling the print device drivers had no effect. Any suggestions?