There is no problem watching this live video in Full screen mode. The web-site sets the allowfullscreen parameter of JW Player incorrectly. Instead of using "yes" they should use "true".
You may copy the following code
Code:
<object type="application/x-shockwave-flash" data="http://www.7rm.es/flashjw/player.swf" width="300" height="260">
<param name="flashvars" value="&file=7rm&streamer=rtmp://directo.redctnet.com/live&type=rtmp&autostart=true" />
<param name="movie" value="http://www.7rm.es/flashjw/player.swf" />
<param name="allowscriptaccess" value="always" />
<param name="quality" value="high" />
<param name="allowfullscreen" value="true" />
<a href="http://get.adobe.com/es/flashplayer/" target="_blank" title="(abre en ventana nueva)"><img src="http://www.7rm.es/img/flashplayer2.gif" alt="Descarga Flash Player" title="Descarga Flash Player" /></a>
</object>
into an HTML file and open it in your web-browser. The Full screen button will allow you to watch the stream in full screen.
But I suggest you to contact 7rm.es and ask them to fix the error.