With several inactive users, applying the 'Hide Inactive' filter on the Manage Users page produces this error:

Database query failed. Error received from database was 0001064: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '?) - TO_DAYS(last_visit) < '7')
ORDER BY username ASC LIMIT 0,50' at line 3 for the query: SELECT *
FROM mantis_user_table
WHERE (1 = 1) AND (TO_DAYS(?) - TO_DAYS(last_visit) < '7')
ORDER BY username ASC.