Error raro con la db

Hola Chicos, tengo Vbulletin 3.6.7

Cuando voy a la "Lista de usuarios" me tira el siguiente error:

Database error in vBulletin 3.6.7:

Invalid SQL:

SELECT user.*,usertextfield.*,userfield.*, user.userid, options,
IF(displaygroupid=0, user.usergroupid, displaygroupid) AS displaygroupid, infractiongroupid
,IF((NOT(options & 1024) AND (user.usergroupid IN (-1,6) OR FIND_IN_SET('6', membergroupids))), 0, reputation) AS reputationscore
,avatar.avatarpath,NOT ISNULL(customavatar.userid) AS hascustomavatar,customavatar.dateline AS avatardateline, customavatar.width AS avwidth, customavatar.height AS avheight
,customprofilepic.userid AS profilepic, customprofilepic.dateline AS profilepicdateline, customprofilepic.width AS ppwidth, customprofilepic.height AS ppheight
, lastactivity AS lastvisittime
, IF(YEAR(user.birthday_search) > 0 AND user.showbirthday IN (1,2) AND user.birthday_search < CURDATE(), user.birthday_search, '0000-00-00') AS agesort


FROM portal_user AS user
LEFT JOIN portal_usertextfield AS usertextfield ON(usertextfield.userid=user.userid)
LEFT JOIN portal_userfield AS userfield ON(userfield.userid=user.userid)
LEFT JOIN portal_reputationlevel AS reputationlevel ON(user.reputationlevelid=reputationlevel.reputationlevelid)
LEFT JOIN portal_avatar AS avatar ON(avatar.avatarid = user.avatarid) LEFT JOIN portal_customavatar AS customavatar ON(customavatar.userid = user.userid)
LEFT JOIN portal_customprofilepic AS customprofilepic ON (user.userid = customprofilepic.userid)


WHERE 1=1
AND (user.usergroupid IN (-1,6,9,11,10,7,5,2))

ORDER BY user.username asc
LIMIT 0, 50;

MySQL Error : Illegal mix of collations (latin1_swedish_ci,COERCIBLE) and (utf8_general_ci,IMPLICIT) for operation 'find_in_set'
Error Number : 1267
Date : Thursday, May 29th 2008 @ 06:38:00 PM
Script : http://www.*******.com/memberlist.php
Referrer : http://www.*******.com/index.php?
IP Address : *********
Username : ****
Classname : vb_database


Alguna idea?, muchas gracias!