Error Code: 850966

Zend_Form_Exception: Invalid validator provided to addValidator; must be string or Zend_Validate_Interface in /home/yourshowbooks/web/yourshowbooks.com/html/application/libraries/Zend/Form/Element.php:1209
Stack trace:
#0 /home/yourshowbooks/web/yourshowbooks.com/html/application/libraries/Zend/Form/Element/Captcha.php(126): Zend_Form_Element->addValidator()
#1 /home/yourshowbooks/web/yourshowbooks.com/html/application/libraries/Zend/Form.php(1151): Zend_Form_Element_Captcha->__construct()
#2 /home/yourshowbooks/web/yourshowbooks.com/html/application/libraries/Engine/Form.php(263): Zend_Form->createElement()
#3 /home/yourshowbooks/web/yourshowbooks.com/html/application/libraries/Zend/Form.php(1060): Engine_Form->createElement()
#4 /home/yourshowbooks/web/yourshowbooks.com/html/application/libraries/Engine/Form.php(247): Zend_Form->addElement()
#5 /home/yourshowbooks/web/yourshowbooks.com/html/application/modules/Sestutorial/Form/Askquestion.php(82): Engine_Form->addElement()
#6 /home/yourshowbooks/web/yourshowbooks.com/html/application/libraries/Zend/Form.php(239): Sestutorial_Form_Askquestion->init()
#7 /home/yourshowbooks/web/yourshowbooks.com/html/application/libraries/Engine/Form.php(146): Zend_Form->__construct()
#8 /home/yourshowbooks/web/yourshowbooks.com/html/application/modules/Sestutorial/controllers/IndexController.php(146): Engine_Form->__construct()
#9 /home/yourshowbooks/web/yourshowbooks.com/html/application/libraries/Zend/Controller/Action.php(516): Sestutorial_IndexController->askquestionAction()
#10 /home/yourshowbooks/web/yourshowbooks.com/html/application/libraries/Zend/Controller/Dispatcher/Standard.php(308): Zend_Controller_Action->dispatch()
#11 /home/yourshowbooks/web/yourshowbooks.com/html/application/libraries/Zend/Controller/Front.php(954): Zend_Controller_Dispatcher_Standard->dispatch()
#12 /home/yourshowbooks/web/yourshowbooks.com/html/application/modules/Core/Bootstrap.php(89): Zend_Controller_Front->dispatch()
#13 /home/yourshowbooks/web/yourshowbooks.com/html/application/libraries/Engine/Application.php(160): Core_Bootstrap->run()
#14 /home/yourshowbooks/web/yourshowbooks.com/html/application/index.php(286): Engine_Application->run()
#15 /home/yourshowbooks/web/yourshowbooks.com/html/boot.php(47): include('...')
#16 /home/yourshowbooks/web/yourshowbooks.com/html/index.php(24): Engine_Boot->boot()
#17 {main}