Some users
report problems with CLoD - freezes - after install this update (KB2670838 - 02/27) for Windows7/8, with some new instructions for DirectX 11.
Happened to me, uninstalled KB2670838 and testing CloD now.
Edit - No uninstall need, just atualize CloD DirectX drivers, from:
...\Steam\steamapps\common\IL-2 Sturmovik Cliffs of Dover\redist\DirectX
Run DXSETUP.exe.
Done here and all OK now.
Sokol1