Graphics corruption of this kind is often seen with highly complex addons.  The system simply can't cope.  There is a fix you can put in the fsx.cfg file.  Go to avisim and search for HIGHMEMFIX=1 .  There are many threads.  It solved all my problems of this nature.  There are numerous other associated mods, but the HIGHMEMFIX=1 line is all you need, plus deleting some files relating to the shader cache, whatever that is.  Here is one thread telling you how to do it:


http://forum.avsim.net/topic/280688-graphics-corruption-in-fsx-update-possible-solution-found/