SQL-DATABASE ERROR

Invalid SQL: INSERT INTO sessions (userid,username,groupid,time,hash) VALUES ('0', 'Gast', '0', '1406775896', '43fc9574cceb3479c144d81fd9a8ced0')mysql error: Table './pdsl_main1/sessions' is marked as crashed and should be repaired
mysql error number: 145
mysql version: 5.1.73
php version: 5.3.3
Date: 31.07.2014 @ 02:34
Script: /index.php
Referer: