Mage registry key "umm_top_menu_exists" already exists

#0 /dati/www/natur-vista.com/public_html/app/Mage.php(223): Mage::throwException('Mage registry k...')
#1 /dati/www/natur-vista.com/public_html/app/design/frontend/ultimo/default/template/infortis/ultramegamenu/mainmenu.phtml(54): Mage::register('umm_top_menu_ex...', true)
#2 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Core/Block/Template.php(241): include('/dati/www/natur...')
#3 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Core/Block/Template.php(272): Mage_Core_Block_Template->fetchView('frontend/ultimo...')
#4 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Core/Block/Template.php(286): Mage_Core_Block_Template->renderView()
#5 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Core/Block/Abstract.php(923): Mage_Core_Block_Template->_toHtml()
#6 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Core/Block/Text/List.php(43): Mage_Core_Block_Abstract->toHtml()
#7 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Core/Block/Abstract.php(923): Mage_Core_Block_Text_List->_toHtml()
#8 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Core/Block/Abstract.php(641): Mage_Core_Block_Abstract->toHtml()
#9 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Core/Block/Abstract.php(585): Mage_Core_Block_Abstract->_getChildHtml('topMenu', true)
#10 /dati/www/natur-vista.com/public_html/app/design/frontend/ultimo/default/template/page/html/header.phtml(21): Mage_Core_Block_Abstract->getChildHtml('topMenu')
#11 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Core/Block/Template.php(241): include('/dati/www/natur...')
#12 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Core/Block/Template.php(272): Mage_Core_Block_Template->fetchView('frontend/ultimo...')
#13 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Core/Block/Template.php(286): Mage_Core_Block_Template->renderView()
#14 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Core/Block/Abstract.php(923): Mage_Core_Block_Template->_toHtml()
#15 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Core/Block/Abstract.php(641): Mage_Core_Block_Abstract->toHtml()
#16 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Core/Block/Abstract.php(585): Mage_Core_Block_Abstract->_getChildHtml('header', true)
#17 /dati/www/natur-vista.com/public_html/app/design/frontend/ultimo/default/template/page/2columns-right.phtml(24): Mage_Core_Block_Abstract->getChildHtml('header')
#18 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Core/Block/Template.php(241): include('/dati/www/natur...')
#19 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Core/Block/Template.php(272): Mage_Core_Block_Template->fetchView('frontend/ultimo...')
#20 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Core/Block/Template.php(286): Mage_Core_Block_Template->renderView()
#21 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Core/Block/Abstract.php(923): Mage_Core_Block_Template->_toHtml()
#22 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Core/Model/Layout.php(555): Mage_Core_Block_Abstract->toHtml()
#23 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(390): Mage_Core_Model_Layout->getOutput()
#24 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Cms/Helper/Page.php(137): Mage_Core_Controller_Varien_Action->renderLayout()
#25 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Cms/Helper/Page.php(52): Mage_Cms_Helper_Page->_renderPage(Object(Mage_Cms_IndexController), 'no-route')
#26 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Cms/controllers/IndexController.php(75): Mage_Cms_Helper_Page->renderPage(Object(Mage_Cms_IndexController), 'no-route')
#27 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(418): Mage_Cms_IndexController->noRouteAction()
#28 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action->dispatch('noRoute')
#29 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Core/Controller/Varien/Front.php(172): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#30 /dati/www/natur-vista.com/public_html/app/code/core/Mage/Core/Model/App.php(365): Mage_Core_Controller_Varien_Front->dispatch()
#31 /dati/www/natur-vista.com/public_html/app/Mage.php(684): Mage_Core_Model_App->run(Array)
#32 /dati/www/natur-vista.com/public_html/index.php(85): Mage::run('', 'store')
#33 {main}