Please have a look here:
Vegas 3D problems
I get this phenomenon when using 3D Source Alpha --> Track Motion and then moving the track slightly in 3D space.
As long as the track is plain 2D, all is fine. I can rotate it, no problem.
But skewing it even the slightest bit, makes half of the image disappear. Either vertically, horizontally or diagonally, as on my sample.
Have I missed something? I think I remember that all was fine when firing up Vegas 3 days ago for the first time.
Newest drivers for DirectX and my Nvidia are installed.