You could be right, I only checked it in FF.It's possible that it may work in firefox, but not IE. Or Chrome.
It seems to work ok for me if I use a negative z-index to put it under some other element. Technically a z-index of less than 0 is actually behind the page layer, so perhaps that has something to do with it.The vlc plugin does not obey z-index. You cannot place anything over it.