The Firefox search bar has been the source of constant annoyance recently. Whenever I was using it, google woudn't behave as expected - all google & igoogle settings weren't applied to the results page, plus the results were served from Google Switzerland. Similar to the situation, when you don't accept the google cookie.
Believe me, I almost freaked - Google Switzerland behaves like crap, compared to google.com, nope I won't go into details here.
The cure to all this was not to choose "Manage Search Engines" within Firefox (100% futile and sterile since ff3) , but to head over to the Mycroft Project as in the old FF days. You'll find gazillions of ready to use FF search engines.
I installed "Google Search (En any unfiltered 100)" and all my problems were solved at once.