Did you try to create a new desktop shortcut?

Check that Firefox isn't set to run as Administrator. Right-click the Firefox desktop shortcut and choose "Properties". Make sure that all items are deselected in the "Compatibility" tab of the Properties window.

• Privilege Level: "Run this program as Administrator" should not be selected
• "Run this program in compatibility mode for:" should not be selected

Also check the Properties of the firefox.exe program in the Firefox program folder (C:\Program Files\Mozilla Firefox\).

If you use a non standard windows theme or made other appearance changes then try to revert those changes and use a (different) standard theme or Windows wallpaper.

• Control Panel > Personalization > Theme & Window Color and Appearance

You can check if there is an update for your graphics display driver and check for hardware acceleration related issues.

• https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration

bobbymo said

I have been having a problem with Firefox and I am wondering if you can help me. I am using Windows 7. I have version Firefox 38.0.5. The desktop icon has a shield like it needs to update and it always opens the user account control box. When Firefox is open the minimize, maximize and close buttons are blacked out in a black rectangle. The buttons still work but I have to guess where they are. I did a full uninstall and removed the remaining files and reinstalled from scratch. It did not help. Do you have any suggestions?

Thanks Cor-el, I will try them