I've got an HP 4795 printer connected to a Windows computer. This printer has worked fine with the computer for several years. It has fresh cartridges in it and the HP GUI says the cartridges are full, yet it is printing blank pages. I have tried running all the alignment tools in the GUI, rebooting the computer, power cycling the printer as well as removing and reinserting the cartridges. I even removed the cartridges and touched their print head on a piece of paper and observed ink. But it is still printing blank pages. Any thoughts?