Install Flash Plugin for Firefox installed from tar.bz2 archive

If you have installed Firefox from the official download (firefox--.tar.bz2) at /opt or similar location and if you are using 64bit version of Linux, then the 64 bit version of Flash Player will not work with Firefox. The solution is to use 32bit version of flash plugin. Here is how you do in Yum based systems:

# rpm -ivh http://linuxdownload.adobe.com/linux/i386/adobe-release-i386-1.0-1.noarch.rpm 
# yum remove flash-plugin
# yum --disablerepo=adobe-linux-x86_64 --enablerepo=adobe-linux-i386  install flash-plugin

If you have a running Firefox window, restart it and you will get your flash plugin back. Tested on CentOS 6.2.