Help! Texture missing...

I had to reinstall XP the other day and then FSX/Accel pack, etc. Now I have one or two planes that have missing textures. One has just a few missing...when you look down the intake or exhaust you can see daylight, but when looking from the outside it's fine. Another plane is missing almost all of the outside texture; all you see with the spinner or in game is just a few parts of the inside of the aircraft...cockpit, landing gear etc. Most of the planes appear to work but these two won't. They worked fine before. I have reinstalled both planes and played with the graphic settings but nothing works. The texture files are there and they can be opened up just fine. Just for some reason in the game, they are either transparent on one side or completely transparent. These are add on planes. What could be causing this?