Wow!  I made a model in Raydream 3D saved it as an .obj and it came up just fine in Carrara 5 Pro.  Even converted several splines to vertex using Carrara 5 Pro vextex modeling room.  Can you save the .obj as a .car in Carrara 4 and bring the .car aboard Carrara 7?  It is very possible that the .obj is defective.  Jan