HP IIISi: "50 SERVICE"

I was printing on my IIISi tonight and, between jobs, it switched from working normally to displaying "50 SERVICE" (with the "50" flashing) and not accepting print jobs. Power cycling doesn't help. I've done a little poking around, but haven't managed to find a service manual for the silly thing. Bitsavers has only one file under hp/printers/, and that one doesn't cover the IIISi. Google finds another file which covers a few III printers, but not the IIISi. Anyone have the manual, or at least have some idea what "50 SERVICE" means I need to do? (What is it with this week and hardware? I'm beginning to feel as though any hardware I try to use this week breaks.) /~\ The ASCII der Mouse \ / Ribbon Campaign X Against HTML mouse at rodents.montreal.qc.ca / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B