How did you "drag and drop" the model into archiCAD? editing third party models can get a bit tricky if they're not formatted for use in archicad - you may be able to change textures and materials, but you may not be able to use more than one material for the entire object.
also you shouldn't be trying to drag the object into the 3d window - it should just appear in the 3D window - try placing a camera in front of the object, select the camera and then go to 3D. try using the AC11 local library before jumping into 3rd party objects...