(Seemingly) Random Missing Scenery Textures

I recently loaded FS9 and noticed the simulator was initializing new, or newly deleted scenery. When I fired up a flight at KCLT, I noticed white blocks in the place of trees and a blank, white sky. I loaded TNCM and the same issue. I then searched for KIAD and noticed it wasn't in the database. The only recent change I have made was to my FMCWP\NAVDATA because my PMDG 747 wasn't picking up the new 0901 AIRAC. Long story short, it's obvious I'm missing some default textures, or in this case even a few Activesky textures, but what would have caused this? And why is KIAD suddenly missing from my airport database?