I had a similar problem with a 'SerialNumberJob' stuck in a print queue for a printer that was installed to LPT1 while a different printer was actually connected to LPT1. The system started REALLY crawling, and the job couldn't be deleted, and the printer couldn't be deleted. Everything came back to normal when the LPT1 device was unplugged. Suddenly the printer's one job deleted, the printer deleted, and the system was running smooth again.
source:
http://www.annoyances.org/exec/forum/winxp/1178138725?s