Getting Datbase Error

[p@ndu]

while opening my forum i am getting this error

Database error in vBulletin 4.0.6:

Invalid SQL:

SELECT *
FROM thread AS thread
LEFT JOIN force_read_users AS force_read_users ON (thread.threadid = force_read_users.force_read_threadid AND force_read_users.force_read_userid = '2')
WHERE thread.force_read = '1' AND (thread.force_read_expire_date = '0' OR thread.force_read_expire_date > '1287029278') AND (force_read_usergroups = '' OR force_read_usergroups LIKE '%-6-%') AND (force_read_forums = '') AND force_read_users.force_read_userid IS NULL
ORDER BY force_read_order ASC;

MySQL Error : Table './*******_downloadsmasti/thread' is marked as crashed and should be repaired
Error Number : 145
Request Date : Wednesday, October 13th 2010 @ 11:07:58 PM
Error Date : Wednesday, October 13th 2010 @ 11:07:58 PM

Referrer :
IP Address : ********
Username : *****
Classname : vB_Database
MySQL Version : 5.1.50

can some one please give em a solution for this