Surprise with "customer/account/loginPost/" at the end of your magento's URL

gistfile1.txt

Warning: array_key_exists() expects parameter 2 to be array, null given  in /var/www/magento/app/code/core/Mage/Captcha/Model/Observer.php on line 69

#0 [internal function]: mageCoreErrorHandler(2, 'array_key_exist...', '/var/www/magent...', 69, Array)
#1 /var/www/magento/app/code/core/Mage/Captcha/Model/Observer.php(69): array_key_exists('username', NULL)
#2 /var/www/magento/app/code/core/Mage/Core/Model/App.php(1338): Mage_Captcha_Model_Observer->checkUserLogin(Object(Varien_Event_Observer))
#3 /var/www/magento/app/code/core/Mage/Core/Model/App.php(1317): Mage_Core_Model_App->_callObserverMethod(Object(Mage_Captcha_Model_Observer), 'checkUserLogin', Object(Varien_Event_Observer))
#4 /var/www/magento/app/Mage.php(447): Mage_Core_Model_App->dispatchEvent('controller_acti...', Array)
#5 /var/www/magento/app/code/core/Mage/Core/Controller/Varien/Action.php(532): Mage::dispatchEvent('controller_acti...', Array)
#6 /var/www/magento/app/code/core/Mage/Core/Controller/Front/Action.php(64): Mage_Core_Controller_Varien_Action->preDispatch()
#7 /var/www/magento/app/code/core/Mage/Customer/controllers/AccountController.php(62): Mage_Core_Controller_Front_Action->preDispatch()
#8 /var/www/magento/app/code/core/Mage/Core/Controller/Varien/Action.php(408): Mage_Customer_AccountController->preDispatch()
#9 /var/www/magento/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(250): Mage_Core_Controller_Varien_Action->dispatch('loginPost')
#10 /var/www/magento/app/code/core/Mage/Core/Controller/Varien/Front.php(176): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#11 /var/www/magento/app/code/core/Mage/Core/Model/App.php(354): Mage_Core_Controller_Varien_Front->dispatch()
#12 /var/www/magento/app/Mage.php(683): Mage_Core_Model_App->run(Array)
#13 /var/www/magento/index.php(87): Mage::run('', 'store')
#14 {main}

Did you ever figure it out?