I am running FSX with DX10 fixer v. 2.4 with Nvidia driver 344.48 on a GTX 550 Ti, Windows 8.
When the visibility is in the foggy range I get dark apron textures and dark clouds that shine through the fog (obviously the don't become faded out by the fog, thus the stick out more with increasing distance).
I tried nearly all combinations of options in the Fixer, but only disabling the general shader restores the normal behaviour (but introduces other errors, of course).
It may be a driver problem, as I did not have this issue a year ago (when I run the 331.82 driver, but also an older DX10 fixer).
dark apron and clouds visible through fog:
General shader disabled - apron and clouds correctly fogged (ORBX lights don't show right)