Printer queue not clearing after a print

I support a small network. OS are WIN98, W2K and XP. On the W2K and XP, 3 users complains when ever they print to printer server after the print job is completed the printer queue does not clear automatically. It needs to be cleared manually, if not the next day they come in the office. As soon as they boot up in the morning a bunch of print jobs from the previous day will start to print by it self. Now, I deleted the printer driver on each station, and hoping it was just a corrupted driver. Reinstalled the driver, tried setting printer priorities and still doing the same thing. What can be the problem ?