IntelliJ Ultimate 14 find usages not working

Question

I am using Intellij IDEA 14 Ultimate. When I search find usages, in find view there is a info like

Searching for usages in project files\" and doesn\'

Answer 1

I had exactly the same problem, so for people looking for the quick answer, try

File -> Invalidate Caches / Restart

Thanks to user @yole and his comment.