Mage registry key “_singleton/core/resource” already exists in magento

Question

I am facing this problem on my site Mage registry key \"_singleton/core/resource\" already exists, Please help me how to solve this error.

I have checked the folder and

Answer 1

I can see this being quite old thread, but I came across similar problem today. I have two observers on catalog_product_prepare_save and catalog_product_save_after, both are triggered in one php execution.

It turns out we were using methods from ProductObserver.php file (XXXX_Persona_Model_ProductObserver class) as listeners. It worked fine on Windows and Macs, but was failing with similar message on production (Linux). You guessed it - Linux is case sensitive. Correcting file name to Productobserver.php (and class name accordingly) solved the problem for us.