Jaunty, Firefox, Flash

After upgrading from 8.10 Intrepid to 9.04 Jaunty, flash no longer worked in Firefox. I found the following workaround on this Ubuntu forum thread:

$ sudo apt-get remove flashplugin-* --purge
$ sudo apt-get install flashplugin-nonfree

I am not sure why "reinstalling" the flash plugin does the trick, but I knew that just doing a --reinstall or the above commands without the --purge did not work for me.