This is really strange.
When I put a any object like s sphere, suddenly it disappear, event though it is
exsit when im selecting it, and this is shown as a clue in the upper left corner of the screen
(like an upper point of view).
I had a similar situation when I first installed R12. And though this may not be anything like my situation this might help you to shoot in a new direction. First have you tried uninstall/reinstall? Second my issue turned out to be the particular video card I was using in conjunction with the Maxon software. There was a problem with conflicting software. I turned off the OpenGL in preferences and it started working fine, not the resolution I would have liked, but it showed me that my video card was not compatible with Studio. If these trouble shoots don't work contact Maxon tech support.