Hello,
In the MyGames launcher, next to the "Play" button, there's a little arrow. It's a menu, you'll find the "Verify and fix installed games client files".
If nothing works, i'd suggest you remove Allods Online client from your computer, remove every part of it with
CCleaner, and install the game again.
You can keep your screenshots by moving or copying them to a safe part of your HDD (you'll find them in your "Allods Online/Personal" folder).