With McAfee disabled, delete the db and have Firefly build a new one. If it starts and runs OK then all is good so far.
Restart McAfee and have it run a scan.
If Firefly then breaks, chances are that McAfee has done something to the db (like quarantine it or lock it).
You will then have to list Firefly’s database as an exempt file.
If Firefly crashes during the initial rebuild then you’ve got corrupted metadata in one of the music files. Check the error log.
The db file name will be songs.db or songs3.db depending on which db type you’re using