For example, under some not-yet-well-defined circumstances, the presence of a CMOD line drawing in the background can cause the Earth's dark side to turn bright orange when viewed using the "Basic" and "Multitexture" rendering paths. It looks fine when using the "OpenGL vertex program".
Here's a screen-grab that I did while it was happening. On the left is the failure mode in the Multixture rendering path. On the right is another copy of Celestia using the Multitexture path but without the CMOD line drawing backdrop.
![Image](http://www.lns.cornell.edu/~seb/celestia/orange.jpeg)
It was doing it consistantly when I did the screen grab, but now I can't get it to do it again.
Bob Hegwood has reported a similar problem with his Intel graphcs chip.