Beat the 404's when you're adding a new tab to Magento's system configuration

Whenever you're adding a new tab into the System Configuration screen in Magento, make sure you clear out your session. Even if you've cleared your cache and have 100% correct config files for it, your old ACL will still be in the session.

I've wasted a lot of time trying to find an error in my config XML, when all I needed was to clear my session!