I have come across a solid model which was constructed by someone unknown to me which shows up on my screen black-like a shadow. It has not been colored black, and any attempt to change colors is futile. All of the part's features and sketches are present and editable, and everything shows up in its corresponding drawing. I cannot see any definition unless i select a specific feature, and then I can still only see the definition of that particular feature outlined or shaded in green. Can anyone tell me why this is happening? This is the second model I have found to be this way.