i think restoring .mbl file will do the trick, but i'm not sure that no settings will be affected. backup existing .mbl file (to new backup location) first.
EDIT:
@phred, you are wrong all tags are stored in MB database (at least for caching), and some tags are stored in MB database only.
EDIT 2:
@Joe King, if you succeed, then you will have to re-write tags in tracks by database tags (select all tracks (ctrl+A), tools> advanced> synchonise tags).