The user interface for Movable Type 4 bears little resemblance to that of its predecessor.
While this is generally a positive move people are, by their nature, creatures of habit. If you got used to doing something in one way, then changing the way you do things may come as a minor shock to the system!
While the overall UI has been explained in some detail by the developers the main issues would seem to stem from the blog specific settings and the actual system (global) settings.
In some of the earlier beta releases this distinction may not have been that clear, but thanks to the power of CSS and some nice graphics it's a lot clearer now!
If you haven't done anything odd with your install you should see two very distinct styles depending on which area you are looking at.
The plain black header and light blue dropdowns is for your blog(s), while the black header with graphic and light green (sort of off green) menus are for the system.
Quite simple really :)

