LibreOffice error: "Either another instance of LibreOffice is accessing your personal settings or your personal settings are locked"
According to the LibreOffice docs and this similar Ask Ubuntu Q&amp;A, it stores a .lock file ~/Library/Application Support/libreoffice/4/user on OS X to indicate a session is active and running.

To clean it up:


Make sure no instances of LibreOffice are currently running.
Open the Terminal application
Optional: Check to see if lock file exists, at the prompt type: ls -l ~/Library/Application\ Support/LibreOffice/?/user/.lock
If you see "cannot access" this means the lock file is not present. 
At the prompt type: rm -f ~/Library/Application\ Support/LibreOffice/?/user/.lock
Close the Terminal application
Start LibreOffice