screen turns off after playback

i am having the occasional issue where after playback especially after playback through the file manager window

the screen turns off like it is going into suspend mode

i havent done extensive testing but i think it happens from time to time when playing an episode through the regular library view

i do have it set to turn off the screen after 20 mins idle time but i would assume if it is playing a video it would not think it is idle

btw i am using a nightly frodo build (7 Nov) and using windows 7 x64