Try the reset described here:
http://kb.mozillazine.org/Problems_printing_web_pages#Reset_printer

Seems to have worked. Thanks!

You're welcome.

Please mark this thread as Solved, by using the Helpful button when you are logged in to this forum.

Am having the same problem, and we've tried the reset and tried fully uninstalling FF and files and reinstalling, same problem. Prints from from IE, Chrome.....what else? I see alot of other people out on the web having the same issue. Window 7 64-bit, Firefox 3.6.15 (was 3.6.14), HP color laser printer.

Yes, I've read that the reset only works for a brief time after which the problem recurs. So far I'm still able to print but I don't expect that to last. I'd hate to have to open IE every time I want to print something.

I have this problem also but the reset did not work and I need to print from my online class if this is the way it is going to be give me back the old Fire fox or fix this problem it is not my fault everything was fine until up date to firefiox 4 I guess I will go back to internet explorer let me know when you fix this problem until then you lost me.

Does not work for me no kidding I want to remain with Mozilla what will you do to keep me as your customer or should I say your Guest!

Still not working why did mozilla do such a negative thing

I reset my firefox preference as directed & it worked. It had the wrong value under print.print_printer

I still cannot use my printer even after resetting the printer it does not work it keep reverting back no matter how many times I try. I want to keep using Mozilla Firefox but I guess I will go to Opera seeing how this problem can not be fixed it is ad though this problem did not exist till this upgrade I've been using Firefox for 4 years now this impassable road block Opera, Safari, internet explorer? Confused and upset

Mine reverted to cannot print status even before the Firefox 4 update. Seems like there's no permanent solution other than switching browsers.

When reposting, please post the following information.

Your Operating System - Windows 7 Premium

The version of Firefox - 4.0.1

What printer you are using (as different drivers can cause different problems) - HP 2600n

The symptoms, including error messages (Just saying it won't print is not enough) - I cannot print from Firefox, keep getting "an unknown error occurred while printing."

What steps you have tried, to fix the problem - http://kb.mozillazine.org/Problems_printing_web_pages#Reset_printer (didn't work at all). I also uninstalled firefox and deleted my profile. Then, I re-installed firefox. It still won't print.

And please be polite. - Please and thank you.

I came across the same problem today, also using a 2600N. Window updated the drivers through a Windows update yesterday, so I suspect that's what caused the problem since it was working fine before.

I tried the reset in about:config and that didn't do jack, but I was able to solve it by removing the printer with device manager and then disconnecting it from my PC, plugging it back in, and letting Windows reconfigure it automatically. It works now.

Good luck

The problem is more than the printer,in my experience.I also have the following print options: "print to pdf" freeware , fax," iPrint",and "Microsoft XPS Document Writer",none of which work either.I am using FF 4,Win7,and a Canon Pixma iP4300 printer.I tried all the suggestions in the previous posts to no avail.What makes it worse in my case is the problem is intermittent .Every time I launch FF,I never know if the print function will work or not. I can print in IE without a problem.

Just to let everyone know I upgraded to FF 5 Beta,and the printer problem is gone (so far). The only thing is most of my favourite add-ons are no longer compatible with the new FF release.Oh well..

This solution from ctlaltl33t (above) worked for me when nothing else did. Fast and easy. I turned on my printer, then I deleted my HP 1600 printer from the "devices and printers" list. I unplugged the connection between my computer and the printer and shut down the computer. I restarted the computer and reconnected the cable between the printer and computer and watched the computer find and load the drivers for this "new" printer. It printed properly with no error message.

OS Win 7 Pro 64 bit Mac OS Snow Leopard

Firefox 7.0.1 on both

I never print on paper direct from browser. I usually print as Pdf and edit the data. (I have 3 Printers Brother-laser, HP-Ink and Epson)

When I save the data as pdf, or print as pdf from FF, the following error message appears: "an unknown error occurred while printing" I tried:

1. Uninstall FF (clean the registry also) - did not work. 2. Approach http://kb.mozillazine.org/Problems_printing_web_pages#Reset_printer (didn't work at all). 3. I received my 256 SSHDD and I made a new install of the OS from scratch - (afterwards I installed FF) - same error

4. All other programs for pdf editing and printing or "saving as pdf" work. Opera, Safari, and even FF 4.0 in a Virtual Box install of Ubuntu 11.4 works.

Is there any other approach (excepting the installation of an older version of FF)? Older FF versions

I don't even have print.print_printer in my about:config ?? How can I add it manualy. It's really anoying....

Does not work!