Would you please reply with some more information on this topic. By Filling automatically do you mean you click on a suggestion and it searches it for you, or do you mean it will not automatically select a suggestion for you?

it will automatically make suggests but when you put your cursor on a suggestion it does nothing,,,apparently many people are having this problem and some are moving to explorer or chrome because it is an important feature that did exist on the previous version

I have the same problem. When I attempt to click on a suggested search in the list, it just closes the list of suggestions without filling in the search bar or running a search. If I start Firefox 4 in safe mode with add-ons disabled, this feature works. However, I haven't the time or patience to go through one by one and disable each add-on and extension individually to see if one of them is truly what is causing the problem.