Firefox: An Unknown Error Occurred While Printing

Oh, the dreaded error message when you wanted to print a web page from Firefox in Windows! Often times, simply viewing the properties page of the active printer will fix the problem. If that doesn't work, restarting Firefox sometimes brings back the printing functionality. When all else fails, restarting the machine will do the trick. The problem is, when you want to print a web page that will no longer exist after you've restarted Firefox or the machine, for instance an order confirmation page. Here's a trick that usually fixed the printer error.

The trick involves restarting the Print Spooler service. But, simply restarting the Print Spooler service will not fix the problem all the time. The real trick lies in the extra step after stopping the service and before starting it again. Read on if you want to find out.

1. Go to Start -> All Programs and right-click on Computer and select Manage. This will start the Computer Management application.

2. In Computer Management, go to Computer Management -> Services and Applications and click on Services.

3. Scroll down to find the Print Spooler Service. Right-click on Print Spooler and select Stop from the context menu.

4. Now here's the trick, before starting the Print Spooler service again, go back to Firefox and click on the print button. Since the Print Spooler has stopped, Firefox will no longer be able to find any printers to print to, thus this action will generate an error in Firefox. Fortunately, this can be safely ignored because we already know that we had stopped all applications from seeing any printers by stopping the Print Spooler service. Simply click on the No button when you get the prompt to install printers.

5. After dismissing the error message in Firefox, go back to Computer Management and right-click on Print Spooler again. Select Start from the context menu to put all printers back on service.

One of these tricks usually fixes the printer error in Firefox. If you are aware of other ways to fix this problem, you are more than welcome to contribute in the comments.