NX3 introduces a menu feature called “Personalized menus”. This is similiar to the behavior found on many Windows applications. With this feature only the most used menu options are displayed with an option to show all on the bottom of the menu.
For new users this may be frustrating and some just don’t like this behavior. To turn this option on/off you will need to set the following preference:
Tools -> Customize -> Options (tab) -> Personalized Menus (section)

Toggle “Always Show Full Menus” to remove the menu hidding feature.

The reason I think they have added this functionality to NX is that they want it to work more like a Windows application and simplify the menu’s. Since most begining users will use menus to learn how to do things i’m not sure why they would want it hidden by default. You will also notice in NX3 the menu options are structured differently, It appears that it is setup for new users, and proceed down the menu to complete the feature they are working on. Maybe this feature should be off by default? Regardless of what your thoughts are with personalized menus here is how to turn them off or on.