Install 64-bit pre-release Adobe Flash Player

• http://ubuntuforums.org/showthread.php?t=1081964

Remove previous existing versions of flash player:

sudo apt-get remove --purge flashplugin-nonfree gnash gnash-common mozilla-plugin-gnash 
sudo apt-get remove --purge swfdec-mozilla libflashsupport nspluginwrapper iceape-flashplugin 
sudo apt-get remove --purge iceweasel-flashplugin mozilla-flashplugin firefox-flashplugin 
sudo apt-get remove --purge xulrunner-flashplugin midbrowser-flashplugin xulrunner-addons-flashplugin
sudo rm -f /usr/lib/mozilla/plugins/npwrapper.libflashplayer.so
sudo rm -f /usr/lib/iceweasel/plugins/npwrapper.libflashplayer.so
sudo rm -f /usr/lib/firefox/plugins/npwrapper.libflashplayer.so
sudo rm -f /var/lib/flashplugin-nonfree/npwrapper.libflashplayer.so
sudo rm -f ~/.mozilla/plugins/npwrapper.libflashplayer.so
sudo rm -f /usr/lib/firefox-addons/plugins/npwrapper.libflashplayer.so
sudo rm -f ~/.mozilla/plugins/*flash*
sudo rm -f /usr/lib/firefox/plugins/*flash*
sudo rm -f /usr/lib/firefox-addons/plugins/*flash*
sudo rm -f /usr/lib/mozilla/plugins/*flash*

Download the 64 bit Flash Plugin SQUARE 10.3, from here

• http://labs.adobe.com/downloads/flashplayer10_square.html

Extract "libflashplayer.so" and move it to /usr/lib/mozilla/plugins

Restart firefox, test if it works:

• http://www.adobe.com/software/flash/about