MyBB SQL Error

MyBB has experienced an internal SQL error and cannot continue.

SQL Error:
145 - Table './newforum/mybb_users' is marked as crashed and should be repaired
SELECT u.*, u.username AS userusername, p.*, f.*, eu.username AS editusername FROM mybb_posts p LEFT JOIN mybb_users u ON (u.uid=p.uid) LEFT JOIN mybb_userfields f ON (f.ufid=u.uid) LEFT JOIN mybb_users eu ON (eu.uid=p.edituid) WHERE pid IN('4631','4719','4820','4827','4844','4846','4847','4863','4929','4950') ORDER BY p.dateline