Laser printers are weird. The quality is great, but generally they're also PostScript printers. PostScript is not new technology. In fact it's quite old, and was designed to — among other things — ensure output consistency. Part of that is the fact that PostScript printers have a certain standard subset of fonts built in, including Courier (and others).
Normally all the data for printing with a particular font is sent to the printer at the time of printing. But if you're using plain "Courier" in your screenplay (which you shouldn't be, really) or one of the other standard PostScript fonts, then the printer will use its own built-in font instead. This can cause conflicts.
If you're using plain "Courier" or one of the other standard PostScript fonts and are having issues with printing stopping, not starting, or otherwise just not working correctly, try changing the font. (For instance, you can change the overall font to something like Courier Screenplay using Document > Change Document Font.)
Tags: courier, fonts, printing