Sometimes, after deleting a file outside Visual Studio, the navigation toolbar (ctrl+,) gets stuck.
Reported at http://blogs.msdn.com/b/somasegar/archive/2014/01/20/visual-studio-2013-update-1.aspx#10491653.
Add a file to project, then delete that file but not in the project.
Sometimes, when intellisense fails to update in time, the navigate popup (ctrl+,) can list this false file.
If you try to open this file from navigator, the navigator will go into bug state and remains on screen , unable to close, unable to navigate into any file.
It seems like some internal exception is not caught.
This problem is especially bad with large c++ project.
I turned off the navigator preview option, if that matters.