Buenas , tengo una instalación de magento 1.8.0.0 que al instalar la extensión "layered navigation seo" http://www.magentocommerce.com/magento-connect/layered-navigation-seo-6101.html , me da el siguiente error en el HOME si la instalo , esto es lo que me sale en el log... creo que la tuve instalada y se me debió desinstalar mal.
Alguna forma de reparar esto ???

a:5:{i:0;s:59:"Mage registry key "_singleton/catalog/layer" already exists";i:1;s:4762:"#0 /home/user33/tienda3/app/Mage.php(222): Mage::throwException('Mage registry k...')

	#1 /home/user33/tienda3/app/Mage.php(476): Mage::register('_singleton/cata...', false)

	#2 /home/user33/tienda3/includes/src/Mage_Catalog_Model_Observer.php(273): Mage::getSingleton('catalog/layer')

	#3 /home/user33/tienda3/includes/src/Mage_Catalog_Model_Observer.php(249): Mage_Catalog_Model_Observer->_isActiveMenuCategory(Object(Mage_Catalog_Model_Category))

	#4 /home/user33/tienda3/includes/src/Mage_Catalog_Model_Observer.php(218): Mage_Catalog_Model_Observer->_addCategoriesToMenu(Array, Object(Varien_Data_Tree_Node), Object(Mage_Page_Block_Html_Topmenu), true)

	#5 /home/user33/tienda3/includes/src/__default.php(21352): Mage_Catalog_Model_Observer->addCatalogToTopmenuItems(Object(Varien_Event_Observer))

	#6 /home/user33/tienda3/includes/src/__default.php(21331): Mage_Core_Model_App->_callObserverMethod(Object(Mage_Catalog_Model_Observer), 'addCatalogToTop...', Object(Varien_Event_Observer))

	#7 /home/user33/tienda3/app/Mage.php(447): Mage_Core_Model_App->dispatchEvent('page_block_html...', Array)

	#8 /home/user33/tienda3/includes/src/Mage_Page_Block_Html_Topmenu.php(74): Mage::dispatchEvent('page_block_html...', Array)

	#9 /home/user33/tienda3/app/design/frontend/base/default/template/page/html/topmenu.phtml(34): Mage_Page_Block_Html_Topmenu->getHtml('level-top')

	#10 /home/user33/tienda3/includes/src/__default.php(3336): include('/home/user33/sho...')

	#11 /home/user33/tienda3/includes/src/__default.php(3367): Mage_Core_Block_Template->fetchView('frontend/base/d...')

	#12 /home/user33/tienda3/includes/src/__default.php(3381): Mage_Core_Block_Template->renderView()

	#13 /home/user33/tienda3/includes/src/__default.php(2541): Mage_Core_Block_Template->_toHtml()

	#14 /home/user33/tienda3/includes/src/__default.php(13451): Mage_Core_Block_Abstract->toHtml()

	#15 /home/user33/tienda3/includes/src/__default.php(2541): Mage_Core_Block_Text_List->_toHtml()

	#16 /home/user33/tienda3/includes/src/__default.php(2260): Mage_Core_Block_Abstract->toHtml()

	#17 /home/user33/tienda3/includes/src/__default.php(2204): Mage_Core_Block_Abstract->_getChildHtml('topMenu', true)

	#18 /home/user33/tienda3/app/design/frontend/default/modern/template/page/html/header.phtml(57): Mage_Core_Block_Abstract->getChildHtml('topMenu')

	#19 /home/user33/tienda3/includes/src/__default.php(3336): include('/home/user33/sho...')

	#20 /home/user33/tienda3/includes/src/__default.php(3367): Mage_Core_Block_Template->fetchView('frontend/defaul...')

	#21 /home/user33/tienda3/includes/src/__default.php(3381): Mage_Core_Block_Template->renderView()

	#22 /home/user33/tienda3/includes/src/__default.php(2541): Mage_Core_Block_Template->_toHtml()

	#23 /home/user33/tienda3/includes/src/__default.php(2260): Mage_Core_Block_Abstract->toHtml()

	#24 /home/user33/tienda3/includes/src/__default.php(2204): Mage_Core_Block_Abstract->_getChildHtml('header', true)

	#25 /home/user33/tienda3/app/design/frontend/base/default/template/page/1column.phtml(42): Mage_Core_Block_Abstract->getChildHtml('header')

	#26 /home/user33/tienda3/includes/src/__default.php(3336): include('/home/user33/sho...')

	#27 /home/user33/tienda3/includes/src/__default.php(3367): Mage_Core_Block_Template->fetchView('frontend/base/d...')

	#28 /home/user33/tienda3/includes/src/__default.php(3381): Mage_Core_Block_Template->renderView()

	#29 /home/user33/tienda3/includes/src/__default.php(2541): Mage_Core_Block_Template->_toHtml()

	#30 /home/user33/tienda3/includes/src/__default.php(27704): Mage_Core_Block_Abstract->toHtml()

	#31 /home/user33/tienda3/includes/src/__default.php(13844): Mage_Core_Model_Layout->getOutput()

	#32 /home/user33/tienda3/includes/src/__default.php(11204): Mage_Core_Controller_Varien_Action->renderLayout()

	#33 /home/user33/tienda3/includes/src/__default.php(11119): Mage_Cms_Helper_Page->_renderPage(Object(Mage_Cms_IndexController), 'home')

	#34 /home/user33/tienda3/app/code/core/Mage/Cms/controllers/IndexController.php(45): Mage_Cms_Helper_Page->renderPage(Object(Mage_Cms_IndexController), 'home')

	#35 /home/user33/tienda3/includes/src/__default.php(13872): Mage_Cms_IndexController->indexAction()

	#36 /home/user33/tienda3/includes/src/__default.php(18234): Mage_Core_Controller_Varien_Action->dispatch('index')

	#37 /home/user33/tienda3/includes/src/__default.php(17768): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))

	#38 /home/user33/tienda3/includes/src/__default.php(20368): Mage_Core_Controller_Varien_Front->dispatch()

	#39 /home/user33/tienda3/app/Mage.php(683): Mage_Core_Model_App->run(Array)

	#40 /home/user33/tienda3/index.php(87): Mage::run('', 'store')

	#41 {main}";s:3:"url";s:1:"/";s:11:"script_name";s:10:"/index.php";s:4:"skin";s:7:"default";}

	~  

Graciassss