Although from the start this has seemed like our plant friend may be looking away from the building (or above/below it), there could me a huge number of reasons. I heard a story where an ArchiCAD reseller spent 1/2 an hour on the phone with a client who had positioned his camera smack dab in the middle of a wall!
I have spent a similar amount of time on the phone due to an unexpected cutaway, and more recently was fooled (and embarrassed) by the ol' Image>Elements to Show in 3D. Sometimes it's just too easy.
The list could go on.... minuscule marquee, a VR scene is current, transparent walls in OpenGL, etc, etc, etc.
Please tell us what it is when you find out - my money is that you've turned your back on your model, so to speak...
Cheers,
Link.