iplayer screen saver problem

[mkjuk]

when i watch stuff on the iplayer through the 15 pin output on the back of my laptop the screen goes black every 3 mins and i have to move the cursor or press a key to get the picture back. This happens even if i open the particualr stream using "launch in a new window" It never happens on any other media player such as WMP or VLC. please can someone tell me how to change the settings accordingly ?

thanks