The problem isn't with your scenery. It's with your weather programme. FS9 can display visibility from unlimited right down to nine feet. With visibility less that nine feet, FS9 doesn't know what to do and displays 3D objects in white. The minimum you can normally set your visibility with the FS9 weather function is 0.1km.
I use FSMETAR for my weather and occaisionally I get a poorly formatted METAR for an airfield. FSMETAR gets confused and sends a VISIBILITY=0 message to FS9, which displays the errors you have seen. I put some made-up METAR files into FSMETAR to give a demonstration.
Visiblity set to about 20km;

Visibility set to 50 feet (pretty much pea soup);

Visibility artificially set to zero;

Hope this helps.