Unable watch Youtube in Mozilla Firefox because cannot download Adobe Flash

I cannot open any YouTube video using Mozilla Firefox 7.0.1. It says “You need to upgrade your Adobe Flash Player to watch this video. Download it from Adobe. Upgrade to Flash Player 10 for improved playback performance.” I tried to download Adobe Flash Player 10.3.183.10 while my anti-virus is off by clicking download now at:
https://get.adobe.com/flashplayer/ but nothing is happening. I tried to download it using Down Them All but only flash player Firefox Document is saved to my Downloads file. What else can I do to resolve this issue and be able to watch movie using Firefox?
