XF 1.1 An unexpected error has occurred/other errors


Active member
Intermittently, I get one of three errors on any page of my XF forum.
  1. "An unexpected error has occurred" on white screen
  2. Google Chrome error "Error 139 (net::ERR_TEMPORARILY_THROTTLED): Requests to the server have been temporarily throttled."
  3. 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 Zend/Db/Adapter/Abstract.php at line 753
    Zend_Db_Adapter_Abstract->fetchRow() in XenForo/Model/Thread.php at line 44
    XenForo_Model_Thread->getThreadById() in
    XenForo/ControllerHelper/ForumThreadPost.php at line 152
    XenForo_ControllerHelper_ForumThreadPost->getThreadOrError() in XenForo/ControllerHelper/ForumThreadPost.php at line 74
    XenForo_ControllerHelper_ForumThreadPost->assertThreadValidAndViewable() in XenForo/ControllerPublic/Thread.php at line 41
    XenForo_ControllerPublic_Thread->actionIndex() in XenForo/FrontController.php at line 310
    XenForo_FrontController->dispatch() in XenForo/FrontController.php at line 132
    XenForo_FrontController->run() in /.../index.php at line 13
This error lasts for about ten minutes, and then the forum returns to functioning normally. I have tried disabling the small amount of (updated) addons I have installed, but that doesn't seem to have resolved the issue. Any thoughts?