There are times when you may have edited Magento and inadvertently locked yourself out of the admin panel. Possibly changing some config data directly through the database.
Well, you need to clear the cache but can’t access the admin, so what can you do?
Easy, simply open up your Magento directory and delete / rename the /var/cache folder!
As long as your permissions are set correctly, Magento will automatically create a new cache folder and all will be well in the world.