Do you have mouse gesture extensions installed (Tools > Add-ons > Extensions) ?

Some have been reported to cause the Error Console to appear.

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of your add-ons is causing your problem (switch to the DEFAULT theme: Tools > Add-ons > Themes).

• Don't make any changes on the Safe mode start window.

See Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems and Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems

The problem does not happen in Safe Mode.

When I open in regular mode, the first error (that repeats about 15 times on the Error Console) is:

Failed to load XPCOM component: C:\Program Files (x86)\DigitalPersona\Bin\FirefoxExt\components\el\dpffcli.dll.mui

Perhaps someone can decode this to see if it is the root of the problem.

I found the culprit and it is the Yoono v7.5 add on. As soon as I disabled and restarted the problem did not repeat.

Thanks to all those who replied and gave me the right information to go to Safe Mode and then, to test each extension. I will notify Yoono support of the problem.

This doesn't format very well. Hope it is helpful. Let me know if I need to reformat it somehow:

MSN Toolbar 4.0 false Search Helper Extension 1.0 false DigitalPersona Extension 5.0.0.4248 true ForceField Toolbar 1.5.152.14 true Xmarks 3.9.2 true AI Roboform Toolbar for Firefox 6.10.1 true Google Toolbar for Firefox 7.1.20100830W true Yoono 7.5.0 false TwitterBar 2.9.10 true NoSquint 2.0.3 true Session Manager 0.6.9.1 true Adblock Plus 1.3.1 true Tab Mix Plus 0.3.8.4 true Forecastfox Weather 2.0.2 true InvisibleHand 2.8 true IE View 1.4.5.1 true Java Console 6.0.20 true Java Console 6.0.21 true bit.ly preview 1.272 true Noia 2.0 eXtreme OPT 3.76 true Firefox Sync 1.5.1 true BetterPrivacy 1.48.3 true Java Console 6.0.22 true Search Toolbar 1.2 true

If you have the Web Developer Toolbar installed, do the following to prevent the Error Console from popping up:

(If the Web Developer toolbar is not visible, you can also access the same parameters via the Tools/Web Developer/Options/Options menus in the Firefox menu bar).

1. Click on the "Options" icon in the Web Developer toolbar.

2. Click on "Options" in the drop-down menu.

3. Click on the "Miscellaneous" icon

4. Make sure that all the boxes are unchecked in the "Warnings and Errors" menu box.

Now the Error console will stop popping up when you go to a site. You can always check the boxes to display the Error Console later if needed.