I installed the same Particles file (smoke mod) & noticed that the sky was overcast but nav officer reported clear skies, I thought that I'd done something to my scene.dat file, fiddled for ages but couldn't find the problem!
At a last ditch effort I disabled the smoke mod containing the particles.dat file as this was the last mod I had installed & fixed the problem!
I didn't think this was tied in but it must be! I was also fiddling with the lightning tga files that are effected by the scene.dat file! Amazing how the various files are tied in and can easily fix one thing & wreck another!