RTSP with Firefox on windows XP doesn't work

[os57741]

I am trying to run VOD over RTSP from a Firefox browser.
The server is working well when I connect with the VLC player.

The VLC plugin is installed and known to FF.

I have added an entry to about:config
network.protocol-handler.app.rtsp > C:\\VLC\\vlc.exe
(I also tried C:\VLC\vlc.exe)

When I enter in FF
rtsp://videoserver:5554/test
I get the following message
Firefox doesn't know how to open this address because hte protocol rtsp is not assoicated with any program.

What am I doing wrong ?
Hope anybody can help me out.