||Until ESRI actually completes its rewrite of the GDI, don't expect this to get better. I now consider ArcScene/ArcGlobe shareware because it's almost impossible to get any decent output from it. I logged an incident request about my problems 2 years ago and nothing has changed (this includes even meeting with the programmers at the conference).
In my situation, once I specify a certain pixel width for the output image (~1100 pixels), the resulting image contains artifacts in it. Either there are black "nodata" squares (see attached) or portions of the image repeat itself in random locations.
It's absolutely frustrating and I'm going to start looking into other 3D alternatives because I don't really have the time to wait for ESRI to fix it.