I just had an issue with the path prefix in a translated site I made. The problem was that the path to the player file was '/en/sites/all/themes/themename/player.swf', but it had to be '/sites/all/themes/themename/player.swf'.
The problem is in the url function that creates the path to the player that prepends the language prefix to the path. While it is a fixed path, set by the user, or the base path, my believe is that the url function is not needed here.
When I removed it, it all worked fine again.
I've included my patchfile to this post.