'''Try Firefox Safe Mode''' to see if the problem goes away. Safe Mode is a troubleshooting mode, which disables most add-ons. ''(If you're not using it, switch to the Default theme.)'' * You can open Firefox 4.0+ in Safe Mode by holding the '''Shift''' key when you open the Firefox desktop or Start menu shortcut. * Or open the Help menu and click on the '''Restart with Add-ons Disabled...''' menu item while Firefox is running. ''Once you get the pop-up, just select "'Start in Safe Mode"'' '''''If the issue is not present in Firefox Safe Mode''''', your problem is probably caused by an extension, and you need to figure out which one. Please follow the [[Troubleshooting extensions and themes]] article for that. ''To exit the Firefox Safe Mode, just close Firefox and wait a few seconds before opening Firefox for normal use again.'' ''When you figure out what's causing your issues, please let us know. It might help other users who have the same problem.'' ________________________________________________________________________________ The Reset Firefox feature can fix many issues by restoring Firefox to its factory default state while saving your essential information. Note: ''This will cause you to lose any Extensions, Open websites, and some Preferences.'' To Reset Firefox do the following: #Go to Firefox > Help > Troubleshooting Information. #Click the "Reset Firefox" button. #Firefox will close and reset. After Firefox is done, it will show a window with the information that is imported. Click Finish. #Firefox will open with all factory defaults applied. Further information can be found in the [[Reset Firefox – easily fix most problems]] article. Did this fix your problems? Please report back to us!

A Quick Share Widget extension which had somehow installed itself without my permission seems to have been the cause of this problem in my case.