Upgrade starts, then:

Tue Jun 24 01:21:24 2008: SELECT value FROM config WHERE name = 'db.version'
This appears to be 4.5.11_GA
Redolog Version: 1.22 New Redolog Version: 1.22
Schema upgrade required
Running /opt/zimbra/libexec/scripts/migrate20070614-BriefcaseFolder.pl
Tue Jun 24 01:21:29 2008: Verified schema version 38.
..........Tue Jun 24 01:21:32 2008: DB: UPDATE mboxgroup41.mail_item mi, mailbox mb
SET mi.name = CONCAT('Briefcase - renamed (', mi.id, ' - 1214288488)'),
mi.subject = CONCAT('Briefcase - renamed (', mi.id, ' - 1214288488)'),
mi.mod_metadata = mb.change_checkpoint,
mi.mod_content = mb.change_checkpoint,
mi.change_date = 1214288488
WHERE mi.mailbox_id = 41 AND mi.folder_id = 1 AND
mi.id != 16 AND LOWER(mi.name) = LOWER('Briefcase') AND
mb.id = mi.mailbox_id;: Table 'mboxgroup41.mail_item' doesn't exist

Died at /opt/zimbra/libexec/scripts/Migrate.pm line 361, line 41.
Script failed with code 256: - exiting
UPGRADE FAILED - exiting


I have no idea how to proceed - any suggestions?