This appears to be caused by corrupted Parameter RAM. It appears the system thinks there is something to print, so the Print Monitor is launched. It then determines there is nothing to print, and therefore quits.
While resetting PRAM is a good first step, sometimes it is necessary to disconnect all power from the logic board to completely clear the contents of all circuits. To resolve this issue, remove the battery for a few minutes then reinstall it and everything should work fine.
This situation could also manifest itself in other members of the Power Macintosh family such as the 6100 and 7100.