I had the same issue. Here's the error message. Why Artio doesn't provide any useful information?
Warning: Invalid argument supplied for foreach() in /home/searshk/domains/sears.hk/public_html/app/code/local/Artio/MTurbo/Model/Observer.php on line 43
Trace:
#0 /home/searshk/domains/sears.hk/public_html/app/code/local/Artio/MTurbo/Model/Observer.php(43): mageCoreErrorHandler(2, 'Invalid argumen...', '/home/searshk/d...', 43, Array)
#1 /home/searshk/domains/sears.hk/public_html/app/code/local/Artio/MTurbo/Model/Observer.php(60) : runtime-created function(1) : eval()'d code(7): Artio_MTurbo_Model_Observer->_delTree('/home/searshk/d...', '/home/searshk/d...')
#2 /home/searshk/domains/sears.hk/public_html/app/code/local/Artio/MTurbo/Model/Observer.php(60) : runtime-created function(1): eval()
#3 /home/searshk/domains/sears.hk/public_html/app/code/local/Artio/MTurbo/Model/Observer.php(61): __lambda_func('???if (!Mage::h...', Object(Artio_MTurbo_Model_Observer))
#4 /home/searshk/domains/sears.hk/public_html/app/code/core/Mage/Core/Model/App.php(1207): Artio_MTurbo_Model_Observer->adminLogin(Object(Varien_Event_Observer))
#5 /home/searshk/domains/sears.hk/public_html/app/Mage.php(416): Mage_Core_Model_App->dispatchEvent('admin_session_u...', Array)
#6 /home/searshk/domains/sears.hk/public_html/app/code/core/Mage/Admin/Model/Session.php(101): Mage::dispatchEvent('admin_session_u...', Array)
#7 /home/searshk/domains/sears.hk/public_html/app/code/core/Mage/Admin/Model/Observer.php(55): Mage_Admin_Model_Session->login('admin', 'putian2010', Object(Mage_Core_Controller_Request_Http))
#8 /home/searshk/domains/sears.hk/public_html/app/code/core/Mage/Core/Model/App.php(1207): Mage_Admin_Model_Observer->actionPreDispatchAdmin(Object(Varien_Event_Observer))
#9 /home/searshk/domains/sears.hk/public_html/app/Mage.php(416): Mage_Core_Model_App->dispatchEvent('controller_acti...', Array)
#10 /home/searshk/domains/sears.hk/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(497): Mage::dispatchEvent('controller_acti...', Array)
#11 /home/searshk/domains/sears.hk/public_html/app/code/core/Mage/Adminhtml/Controller/Action.php(152): Mage_Core_Controller_Varien_Action->preDispatch()
#12 /home/searshk/domains/sears.hk/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(407): Mage_Adminhtml_Controller_Action->preDispatch()
#13 /home/searshk/domains/sears.hk/public_html/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action->dispatch('index')
#14 /home/searshk/domains/sears.hk/public_html/app/code/core/Mage/Core/Controller/Varien/Front.php(177): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#15 /home/searshk/domains/sears.hk/public_html/app/code/core/Mage/Core/Model/App.php(304): Mage_Core_Controller_Varien_Front->dispatch()
#16 /home/searshk/domains/sears.hk/public_html/app/Mage.php(596): Mage_Core_Model_App->run(Array)
#17 /home/searshk/domains/sears.hk/public_html/index.php(78): Mage::run('', 'store')
#18 {main}