I have this error since yesterday:
Fatal error: Class 'Varien_Data_Collection_Db' not found in /home/singlesuit/domains/singlesuits.at/public_html/app/code/core/Mage/Core/Model/Resource/Db/Collection/Abstract.php on line 36
I have not changed anything in the webshop. Also I have uploaded the directory "app" again and cleared the cache, no result. Is there someone who can solve this?
Have you checked that your server has not run out of space? Have you cleared your cache folder completely?
If you have not done anything (Like changed any code) then I would suspect that something in your database changed or your hosting provider changed something
What version of Magento are you using?