so how did you install the plugin ?
sudo apt-get install mozilla-plugin-vlc
then restart firefox and type
about:plugins in the URL bar.. you should see the following output..
Code:
VLC Multimedia Plugin
File name: libvlcplugin.so
Version 0.8.6c Janus, copyright 1996-2007 The VideoLAN Team
http://www.videolan.org/
MIME Type Description Suffixes Enabled
audio/mpeg MPEG audio mp2,mp3,mpga,mpega Yes
audio/x-mpeg MPEG audio mp2,mp3,mpga,mpega Yes
video/mpeg MPEG video mpg,mpeg,mpe Yes
video/x-mpeg MPEG video mpg,mpeg,mpe Yes
video/mpeg-system MPEG video mpg,mpeg,mpe,vob Yes
video/x-mpeg-system MPEG video mpg,mpeg,mpe,vob Yes
video/mpeg4 MPEG-4 video mp4,mpg4 Yes
audio/mpeg4 MPEG-4 audio mp4,mpg4 Yes
application/mpeg4-iod MPEG-4 video mp4,mpg4 Yes
application/mpeg4-muxcodetable MPEG-4 video mp4,mpg4 Yes
video/x-msvideo AVI video avi Yes
video/quicktime QuickTime video mov,qt Yes
application/x-ogg Ogg stream ogg Yes
application/ogg Ogg stream ogg Yes
application/x-vlc-plugin VLC plugin vlc Yes
video/x-ms-asf-plugin Windows Media Video asf,asx Yes
video/x-ms-asf Windows Media Video asf,asx Yes
application/x-mplayer2 Windows Media Yes
etc....
etc....