I have just upgraded to 1.2.1 and during the install process I received the following error: Code: Server Error Mysqli statement execute error : Prepared statement needs to be re-prepared Zend_Db_Statement_Mysqli->_execute() in Zend/Db/Statement.php at line 297 Zend_Db_Statement->execute() in Zend/Db/Adapter/Abstract.php at line 479 Zend_Db_Adapter_Abstract->query() in XenForo/Model/Deferred.php at line 103 XenForo_Model_Deferred->defer() in XenForo/Application.php at line 1288 XenForo_Application::defer() in XenForo/Model/Deferred.php at line 211 XenForo_Model_Deferred->runDeferred() in XenForo/Model/Deferred.php at line 321 XenForo_Model_Deferred->_runInternal() in XenForo/Model/Deferred.php at line 255 XenForo_Model_Deferred->runByUniqueKey() in XenForo/Install/Controller/Abstract.php at line 34 XenForo_Install_Controller_Abstract->_manualDeferredRunner() in XenForo/Install/Controller/Upgrade.php at line 216 XenForo_Install_Controller_Upgrade->actionRunDeferred() in XenForo/FrontController.php at line 337 XenForo_FrontController->dispatch() in XenForo/FrontController.php at line 134 XenForo_FrontController->run() in ***path obfuscated***/install/index.php at line 18 I had no problem when I upgraded my dev site (which has the same set-up and add-ons as my main site). One thing I noticed after this error was that, although the front end looked fine, in the ACP the Users screen was blank (I guess some of the admin templates may not have rebuilt?) I have resolved the issue by Rebuilding the Master Data. However, I had to run this process twice as the first time I got the same error. I don't know if this was a problem with my server at the time or if it could be something else? Anyway, I thought I'd share this just in case.