Since this evening we are seeing this error.
First we see this in error log
2013-08-11T18:46:59+00:00 ERR (3): Warning: include(): Filename cannot be empty in app/code/core/Mage/Core/Block/Template.php on line 241
2013-08-11T18:46:59+00:00 ERR (3): Warning: include(): Filename cannot be empty in app/code/core/Mage/Core/Block/Template.php on line 241
2013-08-11T18:46:59+00:00 ERR (3): Warning: include(): Failed opening '' for inclusion (include_path='lib/minify:app/code/local:app/code/community:app/code/core:lib:.') in app/code/core/Mage/Core/Block/Template.php on line 241
and with full exception printing we see the following.
I tried disabling notifications, but don't know where to start (and how this suddenly occurs)
Warning: include(): Filename cannot be empty in app/code/core/Mage/Core/Block/Template.php on line 241
#0 app/code/core/Mage/Core/Block/Template.php(241): mageCoreErrorHandler(2, 'include(): Filename cannot be empty', 'app/code/core/Mage/Core/Block/Template.php', 241, Array)
#1 app/code/core/Mage/Core/Block/Template.php(241): Mage_Core_Block_Template->fetchView()
#2 app/code/core/Mage/Core/Block/Template.php(272): Mage_Core_Block_Template->fetchView('adminhtml/base/default/template/system/cache/notifications.phtml')
#3 app/code/core/Mage/Core/Block/Template.php(286): Mage_Core_Block_Template->renderView()
#4 app/code/core/Mage/Adminhtml/Block/Template.php(81): Mage_Core_Block_Template->_toHtml()
#5 app/code/core/Mage/Adminhtml/Block/Cache/Notifications.php(62): Mage_Adminhtml_Block_Template->_toHtml()
#6 app/code/core/Mage/Core/Block/Abstract.php(863): Mage_Adminhtml_Block_Cache_Notifications->_toHtml()
#7 app/code/core/Mage/Core/Block/Text/List.php(43): Mage_Core_Block_Abstract->toHtml()
#8 app/code/core/Mage/Core/Block/Abstract.php(863): Mage_Core_Block_Text_List->_toHtml()
#9 app/code/core/Mage/Core/Block/Abstract.php(582): Mage_Core_Block_Abstract->toHtml()
#10 app/code/core/Mage/Core/Block/Abstract.php(526): Mage_Core_Block_Abstract->_getChildHtml('notifications', true)
#11 app/design/adminhtml/default/default/template/page.phtml(55): Mage_Core_Block_Abstract->getChildHtml('notifications')
#12 app/code/core/Mage/Core/Block/Template.php(241): include('app/design/adminhtml/default/default/template/page.phtml')
#13 app/code/core/Mage/Core/Block/Template.php(272): Mage_Core_Block_Template->fetchView('adminhtml/default/default/template/page.phtml')
#14 app/code/core/Mage/Core/Block/Template.php(286): Mage_Core_Block_Template->renderView()
#15 app/code/core/Mage/Adminhtml/Block/Template.php(81): Mage_Core_Block_Template->_toHtml()
#16 app/code/core/Mage/Core/Block/Abstract.php(863): Mage_Adminhtml_Block_Template->_toHtml()
#17 app/code/core/Mage/Core/Model/Layout.php(555): Mage_Core_Block_Abstract->toHtml()
#18 app/code/core/Mage/Core/Controller/Varien/Action.php(390): Mage_Core_Model_Layout->getOutput()
#19 app/code/core/Mage/Adminhtml/controllers/DashboardController.php(43): Mage_Core_Controller_Varien_Action->renderLayout()
#20 app/code/core/Mage/Core/Controller/Varien/Action.php(419): Mage_Adminhtml_DashboardController->indexAction()
#21 app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(250): Mage_Core_Controller_Varien_Action->dispatch('index')
#22 app/code/core/Mage/Core/Controller/Varien/Front.php(176): Mage_Core_Controller_Varien_Router_Standard->match(Mage_Core_Controller_Request_Http)
#23 app/code/core/Mage/Core/Model/App.php(354): Mage_Core_Controller_Varien_Front->dispatch()
#24 app/Mage.php(683): Mage_Core_Model_App->run(Array)
#25 index.php(88): Mage->run('default', 'store')