It is possible that the screen is too wide or too high and that the scroll bars and Find bar fall off.
Open the system menu via Alt+Space and see if you can resize that window.
If that works then close Firefox to save that setting.

See also:

• http://kb.mozillazine.org/Resizing_oversize_window

See also:

• http://kb.mozillazine.org/Corrupt_localstore.rdf

That was the problem. Thanks

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