You are having troubles because of your My Web Search Plugin which is malware by any reasonable definition. You should Google it for information and advice as to its removal. To test this you could start Firefox in Safe Mode - Hold Shift key down as you double click on the Firefox icon, ignore the page that opens and continue. If things work O.K. you have at least one problem. With this alert someone may come by with more specific advice. Why are you using Fx6?