Thanks for your input, but you're speaking above my technical wherewithal. The error comes from the HP driver, I think, as it appears in the box that's created if one clicks on the printer icon that appears in the dock while printing.
I'm speculating that printing from Photoshop doesn't utilize the HP Driver (again, this is above my knowledge level) thus the lack of similar errors.
Printing from PS isn't practical for me- I do online retail of specialty prints at volume, and all my print images are 7200x10300. I print at a volume where sending them one at a time to the printer is tedious and time consuming, plus I have to choose which size paper each gets printed on as I either print them full size (24x36) or reduced to 16x24. My workflow is to do a couple of runs every day- like, I'll send 20 prints (all different images) to printer 1 at 16x24 and 10 to printer 2 at 24x36.
I've tried HP Click, PS and QImage but plain ol' Preview is what works best given my particular parameters. I'm always open to suggestions, though. I'm totally self-educated when it comes to large-format printing and I don't know what I don't know.
It's not fine photography. I could get away with a lesser printer but the Z3200s are welcome overkill. Plus, I know how to tear them down, there's a huge online knowledge-base, parts are plentifully available etc etc.