Hi,

You can try deleting the localstore.rdf and sessionstore.* files in the profile folder after exiting Firefox. To open the profile folder via Firefox: Help (Alt + H) > Troubleshooting Information > Show Folder.

Firefox Profile Folder & Files

Please note that deleting sessionstore files would also forfeit the open tabs so you may want to bookmark them. You can Bookmark All Tabs by right-clicking on a tab. For the App tabs you would have to bookmark them individually.

If the problem persist you can also reset Firefox and start afresh.

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:

1. Go to Firefox > Help > Troubleshooting Information.
2. Click the "Reset Firefox" button.
3. Firefox will close and reset. After Firefox is done, it will show a window with the information that is imported. Click Finish.
4. Firefox will open with all factory defaults applied.

Further information can be found in the Refresh Firefox - reset add-ons and settings article.

Did this fix your problems? Please report back to us!

• Use Restore or Maximize in the right-click context menu of the Taskbar icon to set focus to the Firefox application if you do not see the Firefox window.
• Open the system menu of that Firefox window via Alt+Space and see if you can move and resize that window (use the keyboard cursor keys).

If that works then first close all other open Firefox windows and then close Firefox via "File > Exit/Quit" to save that setting.

Your solution using Alt-Space seemed to work, cor-el! Have opened and closed a couple of times now after "maximizing" without a problem. The fact that I often close the app by just right clicking on the app in the tray may be my problem. I will try to use File/Exit from now on but at least I know how to fix if it happens again.