Well, I've had a frustrating weekend with the same problem.
The printed started generating a 49 error code and I followed the suggestion to update the firmware.
So now I get mostly 79 errors with the occassional 49 error. The printer's currently in a reboot loop. What I don't get is any prints.
What's particularly galling is that not only does this firmware lead to the persistent 79 error, HP have removed any sign of the old firmware in order to regress.
This printer's only printed 693 pages, so I'm going to be incredibly annoyed if it's toast.
I've sent a request to HP Support via the website. Still waiting for any response.