Problems with HP DeskJet 400

I am the tech specialist (computer technician) at our local high school. I have been having trouble with about 4 HP DeskJet 400 printers. When a print job is sent to the printer, the cartridge comes to the middle and the change cartridge light blinks. I have tried replacing the cartridge, replacing the printer cable and downloading the latest drivers from the HP web site, but to no avail. Has anyone seen this problem before? Thanks in advance for any help you can offer.