That blank space for the username under this part of the message:
...sure user " closes LibreOffice on host ".
showed up for me when I let my laptop battery run out and abruptly shut down my Windows computer. For that instance I was using 184.108.40.206 (x64) *and was running via QuickStarter.*
I found solutions, here at Ask LibreOffice and at the OpenOffice forum.
Following that on Windows, while the software was not running I went to %appdata%/LibreOffice/4, and deleted the .lock file like this. But you lose your settings and recent files this way.
Hopefully someone could find out the answer without these consequences.