General :: Internet Streaming Media Won't Play In Firefox

on almost every website i've tried with streaming media the media will not play. i don't know if this is something to do with the proxy server i have to use or a lack of plug-ins on firefox or something else entirely. (they're not blocked i can get them on a windows pc on the same network) [url] this one i can play from the command line with mpalyer but in a browser i get 'waiting for video' and the status bar says 'done' [url] this one i have control of the player buttons but it just says 'buffering' and the status bar says 'done'

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on these two i have control of the player but the status bar says 'transfering data' then 'done and nothing plays [url] this one plays! why's it different? videos plays. bbc iplayer crashes firefox. $ uname -a linux seven 2.6.31-20-generic #58-ubuntu smp fri mar 12 05:23:09 utc 2010 i686 gnu/linux $ firefox -v mozilla firefox 3.5.9, copyright (c) 1998 - 2010 mozilla.org

firefox plug-ins
divx web player
helixdna: realplayer g2 plug-in compatible
quicktime plug-in 7.2.0

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i have firefox set with an 'automatic proxy configuration url' i've tried manual as well.