Try "Reseting Firefox to its default state".
That should fix this issue.
- Click the menu button , click and select .
- Click then in the confirmation window that opens. Firefox will close to refresh itself.
- When finished, a window will list your imported information. Click the button. Firefox will open.
- Select whether you want Firefox to restore all or some windows and tabs and click the button.
This may remove your add ons and other customizations such as extension, etc. You may need to add them back after refreshing.