Creative FX5900 Ultra: tv-out problem ...

Hi there.
I recently owned a Creative Blaster FX5900 Ultra board.
Everything works perfect but the tv-out.
In details, when I select by the nView the clone or extension
or dual view mode, I can perfectly see the desktop theme on
the tv. But when I try to play ad movie (divx, wmv or any other
standards) at fullscreen on the tv (Play on my TV option from
the 56.xx nVidia drivers) the tv screen goes black.
As soon as I close the player, then the tv shows the desktop
theme again.

In the past, I owned an FX5700 Ultra VIVO (from XFX) and a
Ti4200 (Creative). Both work perfectly on tv.

Any advice ?
Can you help me ?

Regards

Luigi