For a 64-bit machine flash player was always a problem. I followed the simple instructions on this wiki page, and everything works well

1. Install flashplugin-nonfree package

   # apt-get install flashplugin-nonfree

2. Install the Adove Flash Player:

   # update-flashplugin-nonfree --install

3. Enjoy Youtube or Hulu on your Chromium or Iceweasel browsers.