Video Video Player for Assets Imported from Blender

Hi,

I have problems using the Video Player from Unity3d, probably because I'm a newbie.
I want to use a 360/180 degree video as a background. I'm able to use the video in the Skybox just fine, the problem with the Skybox is that I can't put something into the video. It always looks like the object ist floating above the background video (I have a moving camera).
So I tried to use a sphere or a half-sphere as the target for the video player. If I use assets from Unity3d this works just fine. But If import the asset from Blender (for example the half-sphere) I'm not able to use it as a target for the video player. There is no video-output, the object just appears black.
As this works perfectly for Unity3d objects, I don't think there is something fundamentally wrong with my setup. In my opinion the problem is part of the import process (or export process) from Blender, any settings I can use ?
Any other ideas how to put something into a background video ?