Our 5-yr-old HP2550n color laserjet thinks it's printing, but only blank pages come out. This started after a pdf printed with an entirely red background ((not the first time this has happened, but that's a different problem). Ink levels are fine. We pressed and held "ready" button to get it to print a test page; it printed some blocks of yellow on 1st page, nothing on 2nd page, printed jet-direct configuration on page 3. Pressed "ready" and "cancel" simultaneously; this produced several pages of either one line of garbage or nothing; had to turn printer off to make it stop spitting these out.
We have removed, separately, all printer cartridges and the imaging drum, and restarted the printer several times.
We have MacBook iMac running OSX 10.6.8.
Any help greatly appreciated. This printer has performed perfectly with fairly light use up til now.