Ever had the “Mage registry key “_singleton/core/resource” already exists” error in Magento and can’t get rid of it? First of all, if you search this on Google, don’t believe anything you read in the first 2-3 pages of results (pages > 3 don’t matter anyway, that’s a black hole…). Even found a champ claiming to “solve” the issue by clearing the cache in index.php EVERY TIME a page was loaded… What’s the point in having a cache engine then? Especially if you’re using the EE version!
Anyway, check if you have APC installed on the box and tweak the
apc.shm_size
in the apc.ini file.
Hope this helps anyone.