Hi kakkola,
I'm away from my PC right now, and this may have already been covered (in which case please disregard with my apologies), but here's something to try if not done already:
Navigate to C:/Programs(x86)/Steam/Steam Apps/Common/Il2 Sturmovik Cliffs of Dover
Locate the Launcher.exe file and right click on it
Select the "Properties" tab in the menu pop up
Locate "Enable Desktop Composition" and uncheck it (ie you're disabling Desktop Composition)
Click "Apply" and exit
If you've not tried that already, I hope it helps!
Snapper
__________________
|