Screensaver?!?

I tried several times with the same result.
I have LinVDR correctly installed (appearently), everything works fine.
I leave my PC powered on all the night and it attached on my TV with the SkyStar 1 Fujitsu-Siemens TV-OUT plug.
I can watch a movie with no probs. The I go to sleep and I leave everything as it is.
Okay, the morning after I have a black scree, but it is enough I press Enter Key or another key (volume up, volume down, change chan, etc, etc) and I begin again to see TV.
What can be wrong? Have I a screensaver on my SkyStar TV-OUT?

Thanks in advance.

First of all thanks for the answer.
Is there any method I can use to avoid this happening?
After how many hours does it happens?
If I have a record scheduled does it start recording the program or the black screen?

Thank you very much

Thanks so much.