Firefox covering up gnome panel at top of screen

[drew einhorn]

Probably some configuration setting has been corrupted.

Firefox expands its window at the top of the screen and covers up the
gnome panel.

If I need to get to something on the panel I have to select:  File -> Quit
then cancel an the panel gets exposed.

I can use the panel to do whatever I need to do.
But very soon, but not immediately afterwards the firefox window expands
and covers up the panel once again.

Any idea where the configuration options the control this kind of behavior live?

-- 
Drew Einhorn