After starting up SQL Server Management Studio today, I noticed that CTR+R shortcut for showing and hiding results pane was not working any more.
The issue appears to be a corrupt .vssettings file, as per following Microsoft KB article – http://support.microsoft.com/kb/2860024.
The solution is to reset keyboard options. Go to Tools -> Options -> Keyboard and click on Reset button. This will make CTRL+R shortcut work again.