make sure your history is cleaned every week or 10 days, it can make the browser run really slow and also crash. Look for updates,
Firefox is still the best browser I must say, it just might be a temporary bug, Mozilla does fix bugs regularly as an alternative if I run into problems with Firefox I just switch over and use Google chrome while I wait for an Firefox update, this has happened to me a few times, Google Chrome is the best for searching on Google, just type your keyword search terms into the address bar and away you go.