>The machine that fails has more printers, but the default printer is the same on both (though on the notebook, where this works, it's seeing that printer through the machine where it fails, no direct connection--and I have no idea if I can actually print that way). They seem to be using the same driver for that printer.

Last time I had a nightmare of this sort the printer drivers were identical, but they were relying on some dlls form the system, and those were different versions. Don't remember how it ended, I guess I woke up on time.