I'm using Magento CE 1.7. here is the error I get suddenly, each time I access the "index management" screen (so I canot access it anymore), or each time I try to update a product (so i can't save product anymore) and each time I try to enable/disable a module from the back end:
Indexer model is not defined.
Trace:
#0 /home/webscoot/www/app/code/core/Mage/Index/Model/Process.php(306): Mage::throwException('Indexer model is not defined.')
#1 /home/webscoot/www/app/code/core/Mage/Index/Block/Adminhtml/Process/Grid.php(72): Mage_Index_Model_Process->getIndexer()
#2 /home/webscoot/www/app/code/core/Mage/Adminhtml/Block/Widget/Grid.php(534): Mage_Index_Block_Adminhtml_Process_Grid->_afterLoadCollection()
#3 /home/webscoot/www/app/code/core/Mage/Index/Block/Adminhtml/Process/Grid.php(62): Mage_Adminhtml_Block_Widget_Grid->_prepareCollection()
#4 /home/webscoot/www/app/code/core/Mage/Adminhtml/Block/Widget/Grid.php(626): Mage_Index_Block_Adminhtml_Process_Grid->_prepareCollection()
#5 /home/webscoot/www/app/code/core/Mage/Adminhtml/Block/Widget/Grid.php(632): Mage_Adminhtml_Block_Widget_Grid->_prepareGrid()
#6 /home/webscoot/www/app/code/core/Mage/Core/Block/Abstract.php(862): Mage_Adminhtml_Block_Widget_Grid->_beforeToHtml()
#7 /home/webscoot/www/app/code/core/Mage/Core/Block/Abstract.php(582): Mage_Core_Block_Abstract->toHtml()
#8 /home/webscoot/www/app/code/core/Mage/Core/Block/Abstract.php(526): Mage_Core_Block_Abstract->_getChildHtml('grid', true)
#9 /home/webscoot/www/app/code/core/Mage/Adminhtml/Block/Widget/Grid/Container.php(77): Mage_Core_Block_Abstract->getChildHtml('grid')
#10 /home/webscoot/www/app/design/adminhtml/base/default/template/widget/grid/container.phtml(36): Mage_Adminhtml_Block_Widget_Grid_Container->getGridHtml()
#11 /home/webscoot/www/app/code/core/Mage/Core/Block/Template.php(241): include('/home/webscoot/www/app/design/adminhtml/base/default/template/widget/grid/container.phtml')
#12 /home/webscoot/www/app/code/core/Mage/Core/Block/Template.php(272): Mage_Core_Block_Template->fetchView('adminhtml/base/default/template/widget/grid/container.phtml')
#13 /home/webscoot/www/app/code/core/Mage/Core/Block/Template.php(286): Mage_Core_Block_Template->renderView()
#14 /home/webscoot/www/app/code/core/Mage/Adminhtml/Block/Template.php(81): Mage_Core_Block_Template->_toHtml()
#15 /home/webscoot/www/app/code/core/Mage/Adminhtml/Block/Widget/Container.php(308): Mage_Adminhtml_Block_Template->_toHtml()
#16 /home/webscoot/www/app/code/core/Mage/Core/Block/Abstract.php(863): Mage_Adminhtml_Block_Widget_Container->_toHtml()
#17 /home/webscoot/www/app/code/core/Mage/Core/Block/Text/List.php(43): Mage_Core_Block_Abstract->toHtml()
etc