Be sure to do this (got from another forum and seemed to work for me):
Clear your cache and defrag the game folder:
After applying the patch go to documents\1c softclub\il-2 sturmovik cliffs of dover\cache
You'll see a bunch of file in there and another folder named "shaders". Go into shaders and delete all files in there, but don't delete the folder too. Now go back one level back to the cache folder. Delete all files in there too (remember, except the shaders folder).
Open steam, right click on CoD's icon, select properties and click on the "local files" tab. Now click on "defragment cache files" (this is not the same cache we just deleted in the documents folder, it's steam's way of referring to your actual game folder).
Also, rename Program Files (x86)\Steam\SteamApps\common\il-2 sturmovik cliffs of dover\parts\core\GUI\Logo.Wmv to something else. This is the opening trailer for the game supposedly causes problems with some ATI cards.
Finally, check the epilepsy filter checkbox in game, then disable it again.
