I'm not sure how to completely describe it, but there's this graphics glitch I get in FSX that usually starts out as certain tiles on the ground starting to get a very striped textural appearance.  After awhile, random polygons of water start to appear in random places (usually inside an airport's area, but not on the taxiways or runways--sometimes even the entire airport except for those surfaces).

 

What is the solution for this?

 

 

What is the solution for this?

I'd start with a big sledge hammer!  Maybe not so drastic would be to uninstall any new addons that may be causing

this.  Did it just start doing this or has it just gotten worse over time?

I'm not really sure what the answer to your question is, unfortunately.  I've read somewhere that somebody solved a similar problem by deleting their shader cache, but for me it keeps coming back, and I can't delete my shader cache often enough (I did just at the beginning of a 15-hour long-haul flight last night, and it had come back by the end of that same flight).  I'm not entirely sure it's the shader cache because of this.

 

Could it be that the ORBX FTX Global Iceland demo has somehow messed with my scenery.cfg and caused this in the rest of the world or something?

Like I said, you may want to eliminate any new things you have recently added.  I tried the ORBX Iceland Demo and trash canned it fairly quickly.