Found this bit of info:
"If you updated your DCS from 1.5.8 OpenBeta to 2.5 while retaining the /Saved Games folder and your GFXs appear messed up, please consider deleting /Saved Games/DCS.xxx/fxo/, but before, make sure you have a copy to use as backup later if needed"
I wonder if it's harmful to just do it anyway, just in case?