If you are transferring a Magento site from one server to other, or from your live server to localhost, then you need upload the files backup and then import your database to a newly created database. Then you edit the app/etc/local.xml file for the DB connection info. Now even if you enter al the correct info, it gives such errors, SQLSTATE[28000] [1045] Access denied for user ‘username’@’localhost’ (using password: YES) So, here is a solution to that : Just erase /app/etc/use_cache.ser ...

If you are getting ACCESS DENIED error message, while trying to access SYSTEM > CONFIGURATION, that means, you have just installed something from Magento Connect. When you install a new extension, it’s always better to log out and log back in. It’s using ACL to restrict access based on user privileges. Even if you’re logged in with administrator privileges, it doesn’t recognize you. The only solution to this is to log out and log back in again.  That solves this problem!!...