Printer pauses when printing from MacBook or MacBook Pro

I am having a problem with MacBooks and MacBook Pros causing printers to pause. Occasionally when multiple users attempt to print to one printer (in this case a Xerox Phaser 3600) they get the following error message:

After hitting Resume, they are prompted for administrator credentials. These are high school students who do not have administrator privileges...nor should they need them to print. Any idea what would cause a printer to pause? All these machines are running 10.8. Would it just be the print drivers maybe? I called Xerox and they recommended reinstalling the drivers ...which we have already tried. Any insight would be appreciated. Thanks!