I have had similar problems. In my case, I set my homepage to google in the uk so, when I want to do a search, I go from there.
So, click Tools then Options on the drop-down menu. On the next window, click on "General" tab at the top left. In the space where it asks for your home-page address, delete what is there (if appropriate) and type in the google dot com address dependent on your country etc. Once this is done, click okay at the bottom of this window.
You can then access your homepage by clicking the icon that looks a bit like a house on your tool bar at the top of your FF screen (well, I expect you know this!).
If, for some reason, you don't have the home-page icon, then right-click above the url bar and a drop-down menu will appear. Fins the "House" icon, and drag and drop it onto the second row which is the same row as the URL thing and drop it to the left of this.
It is not a perfect solution, but it is the easiest!
I don't use my url bar at all any more.