zerflin I know what the problem is and it's related to why some older sites wont backup anymore the DB in the backups. You see back when we changed password formats we also changed how sessions are created. As a result in some cases randomly with the old details over time it would disallow some connections. The fix is really simple, change the database password, and the best part is just changing it to the same password it already is resets all permissions.
If you have a Mac you can use a program called Sequel Pro and its free and lets you remote in to databases and makes it easer to work with, but also allows you to run tests.