Your textures.fst file is corrupted, those files should be inside.
If you have MCO take from water0000 to water0015 from any mission and rename.
Rename how high? Mine are starting at 16. Does that mean I need to rename water0000 to 16 and go all the way up to 30?
EDIT: Not enough. I went up to 31 and used all the textures but its still asking for more. Guess its time to make copies.
The thing I don't understand is that there are NO other textures in there at all. These are the first textures to be put in, in fact there wasn't even a texture folder until I copied it across shortly after finding this problem. Why would this problem come up now of all times? I'm at least 15 missions into the game without any prior problems.
EDIT2: This is insane. I am up to 47 and its now asking for 48. Is anyone able to check their files and figure out how high I need to go?