Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of your add-ons is causing your problem (switch to the DEFAULT theme: Tools > Add-ons > Themes).

See Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems and Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems

Hi, You can select the Options button which is the second top button on the right hand side. And then select the radio button next to the "Never show Instant results" caption. I think there is a problem with google's javascript somewhere for firefox. Or if you have the User Agent switcher plugin, you can select "Internet Explorer 7 (Windows Vista)".