Cannot Open Admin Panel - Error log

[MarMorales]

Hello, i have tried to find out what´s goin´ on with my admin, the login page shows this error log:

Mage registry key "_singleton/massemail/observer" already exists

Trace:
#0 /home2/nahuiev1/public_html/app/Mage.php(223): Mage::throwException('Mage registry k...')
#1 /home2/nahuiev1/public_html/app/Mage.php(477): Mage::register('_singleton/mass...', false)
#2 /home2/nahuiev1/public_html/includes/src/__default.php(21770): Mage::getSingleton('massemail/obser...')
#3 /home2/nahuiev1/public_html/app/Mage.php(448): Mage_Core_Model_App->dispatchEvent('core_block_abst...', Array)
#4 /home2/nahuiev1/public_html/includes/src/__default.php(1986): Mage::dispatchEvent('core_block_abst...', Array)
#5 /home2/nahuiev1/public_html/includes/src/__default.php(28179): Mage_Core_Block_Abstract->setLayout(Object(Mage_Core_Model_Layout))
#6 /home2/nahuiev1/public_html/includes/src/__default.php(28195): Mage_Core_Model_Layout->createBlock('adminhtml/page_...', 'head')
#7 /home2/nahuiev1/public_html/includes/src/__default.php(27962): Mage_Core_Model_Layout->addBlock('adminhtml/page_...', 'head')
#8 /home2/nahuiev1/public_html/includes/src/__default.php(27928): Mage_Core_Model_Layout->_generateBlock(Object(Mage_Core_Model_Layout_Element), Object(Mage_Core_Model_Layout_Element))
#9 /home2/nahuiev1/public_html/includes/src/__default.php(27929): Mage_Core_Model_Layout->generateBlocks(Object(Mage_Core_Model_Layout_Element))
#10 /home2/nahuiev1/public_html/includes/src/__default.php(14024): Mage_Core_Model_Layout->generateBlocks()
#11 /home2/nahuiev1/public_html/includes/src/__default.php(13949): Mage_Core_Controller_Varien_Action->generateLayoutBlocks()
#12 /home2/nahuiev1/public_html/includes/src/Mage_Adminhtml_Controller_Action.php(275): Mage_Core_Controller_Varien_Action->loadLayout(NULL, true, true)
#13 /home2/nahuiev1/public_html/app/code/core/Mage/Adminhtml/controllers/IndexController.php(81): Mage_Adminhtml_Controller_Action->loadLayout()
#14 /home2/nahuiev1/public_html/includes/src/__default.php(14098): Mage_Adminhtml_IndexController->loginAction()
#15 /home2/nahuiev1/public_html/includes/src/__default.php(18482): Mage_Core_Controller_Varien_Action->dispatch('login')
#16 /home2/nahuiev1/public_html/includes/src/__default.php(18016): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#17 /home2/nahuiev1/public_html/includes/src/__default.php(20808): Mage_Core_Controller_Varien_Front->dispatch()
#18 /home2/nahuiev1/public_html/app/Mage.php(684): Mage_Core_Model_App->run(Array)
#19 /home2/nahuiev1/public_html/index.php(87): Mage::run('', 'store')
#20 {main}

Any idea what´s this? 

I appreciate any help

Thank you!

[Pronto]

Apparently your massemail extension (whatever it is) is not playing nice. I suggest you disable it manually to get into backend.

[bacac]

I have a similar problem, can someone please help me please

There has been an error processing your request
Mage registry key "_singleton/mageplace_notification/feed" already exists

Trace:
#0 /home/lavander/public_html/web-shop/app/Mage.php(223): Mage::throwException('Mage registry k...')
#1 /home/lavander/public_html/web-shop/app/Mage.php(477): Mage::register('_singleton/mage...', false)
#2 /home/lavander/public_html/web-shop/app/code/core/Mage/Core/Model/App.php(1336): Mage::getSingleton('mageplace_notif...')
#3 /home/lavander/public_html/web-shop/app/Mage.php(448): Mage_Core_Model_App->dispatchEvent('controller_acti...', Array)
#4 /home/lavander/public_html/web-shop/app/code/core/Mage/Core/Controller/Varien/Action.php(527): Mage::dispatchEvent('controller_acti...', Array)
#5 /home/lavander/public_html/web-shop/app/code/core/Mage/Adminhtml/Controller/Action.php(160): Mage_Core_Controller_Varien_Action->preDispatch()
#6 /home/lavander/public_html/web-shop/app/code/core/Mage/Core/Controller/Varien/Action.php(407): Mage_Adminhtml_Controller_Action->preDispatch()
#7 /home/lavander/public_html/web-shop/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action->dispatch('login')
#8 /home/lavander/public_html/web-shop/app/code/core/Mage/Core/Controller/Varien/Front.php(172): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#9 /home/lavander/public_html/web-shop/app/code/core/Mage/Core/Model/App.php(365): Mage_Core_Controller_Varien_Front->dispatch()
#10 /home/lavander/public_html/web-shop/app/Mage.php(684): Mage_Core_Model_App->run(Array)
#11 /home/lavander/public_html/web-shop/index.php(83): Mage::run('', 'store')
#12 {main}

Error log record number: 990154555016