After reading various posts (tru search) regarding uploading flv and even though I have set it in the configuration "Allowed movie types" And I have read the "General Troubleshooting Upload" (Read this thread very carefully. Very, very, carefully.)"
I get no other message that the "Forbidden file extension".
Install this plugin.
http://forum.coppermine-gallery.net/index.php/topic,24186.0.html
As for playing them, there are many mods but I would recommend the Enlarge-it Plugin
http://forum.coppermine-gallery.net/index.php/topic,53290.0.html
All of this can be found easilly with the search function if you search for flv or .flv