Hello there!
I have the same problem as "Der RedMax". But I did not install SweetFX.
Would be great if someone has a solution on this as the sky looks quite creepy. ;)
My system:
Intel i5 2.5GHz (3.1GHz TurboBoost)
8GB RAM
NVIDIA GeForce GT 650M
Windows 7 Professional 64bit
DCS World 1.5.2 (Steam)