This appears to be a problem primarily with Google Toolbar and Firefox 4.

The symptoms are that as you type into Google toolbar's searchbox, a number of similar suggested topics appears in a list under the toolbar searchbox. If you try to use your mouse to select one of the selected topics, unlike with previous versions of Firefox that automatically filled in the searchbox with the selected topic and launched a search Google for it, the searchbox is not automatically filled in with the selected search topic and no Google search occurs.

The workaround that works is to currently to use your keyboard (instead of your mouse) to select the topic from the list of similar search topics. You will need to use your keyboard arrow keys to navigate and highlight the desired topic and then to hit the Enter key to proceed. Doing so populates the Google Toolbar searchbox and initiates a Google search for the desired topic. Results of the search then appear in the window like in previous versions.

See also:

• http://www.google.com/support/toolbar/bin/static.py?page=known_issues.cs

I just tried clicking the left button of the mouse BEFORE placing the pointer above the drop-down arrow of the Google search and worked. If the word was deep down the list, i scrolled down the wheel of the mouse. Always keeping the left button pressed and releasing it once i had pointed my choice.