I got this the other day when I was attempting to search for some text. Nothing had visibly changed that I could see and for some reason the search was always returning ‘No files were found to look in’ regardless of the search options I entered (i.e. types to search, looking in entire solution, project etc).
I cannot explain this but focus on Visual Studio and press Ctrl + Scroll Lock fixes it. Yes it is mad and doesn’t make sense.
Credit goes to: here