Database Error! Need Help ASAP.

[MarcInJapan]

I was thinking maybe my host/server had issues, but only one of my sites is receiving this error. Can't open posts or threads. Chatbox works fine. Here is what I get when I try to open a post or thread:

Database error in vBulletin 3.8.6:

Invalid SQL:

SELECT
IF(votenum >= 1, votenum, 0) AS votenum,
IF(votenum >= 1 AND votenum > 0, votetotal / votenum, 0) AS voteavg,
post.pagetext AS preview,
thread.threadid, thread.title AS threadtitle, thread.forumid, pollid, open, postusername, postuserid, thread.iconid AS threadiconid,
thread.dateline, notes, thread.visible, sticky, votetotal, thread.attach, thread.lastpost, thread.lastposter, thread.lastpostid, thread.replycount, IF(thread.views<=thread.replycount, thread.replycount+1, thread.views) AS views,
thread.prefixid, thread.taglist, hiddencount, deletedcount

, deletionlog.userid AS del_userid, deletionlog.username AS del_username, deletionlog.reason AS del_reason

, threadredirect.expires
, post_user.displaygroupid AS post_user_displaygid, post_user.usergroupid AS post_user_usergid, last_post_user.displaygroupid AS last_post_user_displaygid, last_post_user.usergroupid AS last_post_user_usergid
FROM thread AS thread
LEFT JOIN deletionlog AS deletionlog ON(thread.threadid = deletionlog.primaryid AND deletionlog.type = 'thread')


LEFT JOIN post AS post ON(post.postid = thread.firstpostid)

LEFT JOIN threadredirect AS threadredirect ON(thread.open = 10 AND thread.threadid = threadredirect.threadid)
LEFT JOIN user AS last_post_user ON (thread.lastposter = last_post_user.username)
LEFT JOIN user AS post_user ON (thread.postuserid = post_user.userid)
WHERE thread.threadid IN (0,40817,40462,40312,40576,40527,40424,40416,40358 ,40359,39764,39549,39540,39569,39502,39494,39440,3 9360,39364,39222,39299,39291,39072,39128,39071,390 37,39021,38890,38930,38902,38887,23156,30253)
ORDER BY sticky DESC, lastpost DESC;

MySQL Error : Table './ustangs_united3/post' is marked as crashed and should be repaired
Error Number : 145
Request Date : Tuesday, September 6th 2011 @ 10:41:08 AM
Error Date : Tuesday, September 6th 2011 @ 10:41:08 AM
Script : http://www.unitedstangs.com/forums/forumdisplay.php?f=6
Referrer : http://www.unitedstangs.com/forums/index.php
IP Address : 132.3.57.01
Username : Marcus
Classname : vB_Database
MySQL Version : 5.1.56

Is this something that can be repaired? Am I missing a current patch? Or is this a virus?

Your immediate help is appreciated!