Probably you had already installed browser-plugin-lightspark and/or flashplugin-nonfree. On about:plugin page you see just one at a time. Switch active flash plugin with
$ sudo update-alternatives --config flash-mozilla.so -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
