Yeah, that's a fun one, huh? We had it so that sometimes you'd print 2 copies at the same time and get one from one printer and one from another. Never figured out what caused it. It seemed to resolve itself after a while, still popping up from time to time.
Just to be safer, make sure that you're choosing the right printer both under the print dialog, and then also in the "printer..." sub-dialog that you get from the "printer..." button at the bottom of the print dialog.