This is a problem with one of the following mixups:
8k Atmosphere
16k Atmosphere
Scene.dat
You have probably installed a mod over another, check for any mods associated with these files & remove it, if you don't use the JSGME mod enabler utility I suggest you do, this resolves a lot of problems, can be found in Subsim downloads section.
Hope this is some help.

Cheers.
Edit: Trust you to post at the same time Pants!!