Thank you for the information. I tried a possible solution I had thought of that might have worked with the power button being held down (basically, trying to send the update to the printer before it started that error code), but it didn't work on my unit. (I typrically work on cosumer printers, so I'm somewhat iffy on the business ones.) I guess I should have tried it first before asking you to do that, sorry for wasting your time.
Tomorrow is HP experts day. I'll see if we can get you in touch with a customer satisfaction person.