That happens with me with Real Enviroment Pro on my old nVIDIA 5600 when I have the 'Land and Water' effects slider set to both, rather than land only (in the FS9 display menu). I belive it is because my old card does not support the high level of antiscoptic filtering that the textures require to display.
also if the card has changed in mb ie 128 -256 mb you mite have to change that in the bios , not sure on your card extra but i just thought id mention that ... mike