I finaly found a workaround about my view video window
not showing any playing video..
When I undock the view video window and drag it down
with partialy hiding the bottom under the window taskbar the
video plays clearly in the visible upper region and when I drag it still floating
but all above the taskbar the image stops showing in playback..
WEIRD...
Now I know its not a video codec issue.
The video I found that is accepted is a WMV file 1080x720 6mbps.
I cannot figure what settings I could tweak to get rid of that behaviour
but I can live with that..
BTW my Sonar X3 version is X3a build 211 - x64
I think it's an old version.. I should upgrade !
Thanks everybody !!!