I am using 12.04 Ubuntu 12.04 with Firefox 18. When I used 12.04 Ubuntu with Firefox 17, I didn't have any problems opening radio stream audio files (asf/ram). But since the upgrade to Firefox 18, I can't open these anymore. I checked that all necessary plugins were installed in Firefox 18.
Then I did a re-install of Ubuntu 12.04 and installed all the media software (vlc/mplayer)and media codecs I needed (medibuntu, flash player, w64codec, etc). I also checked that my Firefox has all the media plugins I need (Divx, gecko-mediaplayer plugins, mediaplayerconnectivity 0.95) but I still can't open radio stream audio files online, so I hope someone can help.