If you are using LibreOffice on Mac OS X, you may see an unclosed dialog box "Don't restore windows or Restore windows".
This dialog box cannot be closed even Force Quit. You can only kill the process in command line. Once it happens, will always happens until you reinstall Mac OS (not only LibreOffice).
This is a 100% bugs but never fixed by Libre, poor guy :<
Doing this to help you temporary. Very easy, delete the save state folder and contents by this command:
rm -rf ~/Library/Saved\ Application\ State/org.libreoffice.script.savedState
Okay, now. Open LibreOffice without any problem :>
Bugs information for reference: