A possible cause of this error is that Firefox is set to run as Administrator.

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\).

Non of these things are checked. And it is not clear once you are in the Mozilla folder where to go next. I have a list of Browser, components, defaults etc. C:\Program Files (x86)\Mozilla Firefox\?????????\?????????\

That would be the firefox.exe program.

Note that Windows hides some file extensions by default, so you may only see the name Firefox without file extension. You can check the real file type (file extension) in the Properties of ae file via the right-click context menu in Windows Explorer.

See also my reply here:

• [/questions/981757#answer-531274]