LibreOffice 3.6 is quite old now, assuming you have had this version working previously then there may be a problem caused by one of the recent windows updates.
There was a recent windows defender update that was flagging a false positive virus detection and removing one of the components of LibreOffice, not sure if that might give this error.
Some things you could try:-
1). Download the latest updates for windows defender, then re-install LibreOffice to repair your installation.
2). Restore windows to a restore point when LibreOffice was working. This might also need re-install/repair LibreOffice.
3). Download the latest updates for windows defender, Uninstall your old version of LibreOffice and then install latest Still version.
I’d recommend making a backup of all your files before trying any of the above to make sure you don’t lose anything important.