Hi,
I had this issue and became crazy 2 nights be searching and it was caused by ATI Catalyst 13.9 version and Directx 9 mode Under FSX. (Last Drivers from Microsoft Windows Update is also causing this problem so have to uncheck this one If your computer ask to update this drivers)
If you try this version using DirectX 10 preview mode, there is no problem, If you revert your drivers back to 13.4 it will work.
Hope ATI is aware of that and will fix the issue.
I have tried the 13.11 beta version and the problem is still there.
Regards,