check if libreoffice is running
/opt/alfresco-5.0.a/libreoffice/scripts/libreoffice_ctl.sh status
edit the file /opt/alfresco-5.0.a/alfresco.sh modify the line LIBREOFFICE_SCRIPT with the correct script path
LIBREOFFICE_SCRIPT=$INSTALLDIR/libreoffice/scripts/libreoffice_ctl.sh