Printing junk pages?

4 days ago all my network/shared printers started printing page after page with one or two lines of junk code on top of each page. I rebooted the file and print server and it seemed like it stopped. However since then I have a bunch of personal printers that are not even shared doing the same thing. I am flooded with calls from uses asking me why their printers suddenly start printing junk even though they have not sent a print job to it. Could it be a virus causing that? My Norton AV has not detected anything.