Can you post the full error? It should contain a stack trace:
Admin CP -> Tools -> Server Error Log
Error Info
Zend_Db_Statement_Mysqli_Exception: Mysqli prepare error: Unknown column 'user.user_id' in 'on clause' - library/Zend/Db/Statement/Mysqli.php:77
Generated By: Unknown Account, 37 minutes ago
Stack Trace
#0 /home/admin/domains/myurl/public_html/forum/library/Zend/Db/Statement.php(115): Zend_Db_Statement_Mysqli->_prepare('????SELECT thre...')
#1 /home/admin/domains/myurl/public_html/forum/library/Zend/Db/Adapter/Mysqli.php(381): Zend_Db_Statement->__construct(Object(Zend_Db_Adapter_Mysqli), '????SELECT thre...')
#2 /home/admin/domains/myurl/public_html/forum/library/Zend/Db/Adapter/Abstract.php(478): Zend_Db_Adapter_Mysqli->prepare('????SELECT thre...')
#3 /home/admin/domains/myurl/public_html/forum/library/Zend/Db/Adapter/Abstract.php(753): Zend_Db_Adapter_Abstract->query('????SELECT thre...', 5196)
#4 /home/admin/domains/myurl/public_html/forum/library/XenForo/Model/Thread.php(44): Zend_Db_Adapter_Abstract->fetchRow('????SELECT thre...', 5196)
#5 /home/admin/domains/myurl/public_html/forum/library/XenForo/ControllerHelper/ForumThreadPost.php(152): XenForo_Model_Thread->getThreadById(5196, Array)
#6 /home/admin/domains/myurl/public_html/forum/library/XenForo/ControllerHelper/ForumThreadPost.php(74): XenForo_ControllerHelper_ForumThreadPost->getThreadOrError(5196, Array)
#7 /home/admin/domains/myurl/public_html/forum/library/XenForo/ControllerPublic/Thread.php(33): XenForo_ControllerHelper_ForumThreadPost->assertThreadValidAndViewable(5196, Array, Array)
#8 /home/admin/domains/myurl/public_html/forum/library/Dark/TaigaChat/ControllerPublic/Index.php(8): XenForo_ControllerPublic_Thread->actionIndex()
#9 /home/admin/domains/myurl/public_html/forum/library/XenForo/FrontController.php(310): Dark_TaigaChat_ControllerPublic_Index->actionIndex()
#10 /home/admin/domains/myurl/public_html/forum/library/XenForo/FrontController.php(132): XenForo_FrontController->dispatch(Object(XenForo_RouteMatch))
#11 /home/admin/domains/myurl/public_html/forum/index.php(13): XenForo_FrontController->run()
#12 {main}
Request State
array(3) {
["url"] => string(72) "
http://myurl/forum/threads/"
["_GET"] => array(0) {
}
["_POST"] => array(0) {
}
}
===========
I had to shorten it a little as it was too much text on there.
Thanks!