Generally this manifests itself as the printer not being seen by the computer. There are several common causes of this problem. First is physical misconfiguration, such as loose or incorrectly connected cables. This is usually seen when the PC is first put together.
Problems sometimes result from incorrect printer drivers or incorrect settings.
Also, the use of advanced printer port modes can sometimes cause problems. First of all, make sure that you are testing with a printer that you know works. Also, to test basic connectivity, don't do fancy things like printing color graphics from Windows. Try printing a plain text file for starters. Test the printer on another PC to make sure that it is working correctly.