Downloaded FF6 made it my default browser, started it up and got 7 copies of the browser. Had to manually close 6 and then enter my destination. I had noticed this in FF5 and took it off default, started using Chrome instead. Had problems with it accessing certain types of pages, so switched to IE 9 but really wanted FF so downloaded 6 but found the same problem again with many iterations of the browser starting up.
Also find that if I click on a link in my email FF does not start, I have to manually enter the information for it to go to the URL.