Well it's happened, after 7 years of trouble free flying, I've been invaded by a virus (trojan) and what is more I believe it came with a texture download. Alternately it has copied the original EXE file (Steerman). The file was a whopping 16.7 mb and it was picked up when I selected the Stearman Black Crow from within the sim; quote Agent 12.AF; c\Recycled\DC15EXE unquote. Thankfully it's now tucked away in my virus vault but it has affected scenery but only certain areas and almost without exception in the US. Europe seems to be untouched. What I am seeing now in these affected areas is very large white or grey rectangles almost like the weird slabs which were in the movie 2001 Space Odessey (for those who remember it)
I really don't know where to start to sort this out as my scenery library is so complicated now having installed a very large number of files. I am more than a little reluctant to do a complete re-instal. The problem is not always confined to areas around airports but can crop up anywhere but not everywhere.
I just thought I'd share this with you but at the same time if any one has a solution please let me know.
As ever thanks.

Crocker