Sorry for asking but is this related to AFCS development ?
(i.e. are you trying to view a video stream in an AFCS enabled
application).
Just trying to figure out if AFCS may be involved in blocking
the fullscreen mode.
If you are not using AFCS, then sorry, you are in the wrong
forum :)
(even if in the good old days FMS was called FCS, but that's
another story)