SQL-DATABASE ERROR

Database error in WoltLab Burning Board (2.3.4): Invalid SQL: DELETE FROM bb5_sessions WHERE lastactivity<1283965084
mysql error: Table './usr_web31_1/bb5_sessions' is marked as crashed and should be repaired
mysql error number: 145
mysql version: 5.0.30-Debian_0.dotdeb.1
php version: 5.2.0-0.dotdeb.3
Date: 08.09.2010 @ 19:28
Script: /board/formmail.php?userid=5935
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