The menu bar in OS X is in my view, the nerve center for accessing each and every one of the functions that can be modified by the user to take advantage of system resources, with application-specific menus, general settings and the possibility of add a number of extras to it at the top right such as battery level, VPN status, Bluetooth plus background programs.
Although the power unify everything in a single bar It is an advantage, sometimes there are problems in which the system freezes or blocks due to incompatibilities between different third-party programs such as firewalls, usually only the upper right part will be blocked, and you can still access the File, Edition menus ...
To try to tackle the problem, what we can do is delete preferences file which manages the menu bar, which can help everything work normally.
All we have to do is press the key Alt while we click on the menu Ir in Finder to open the Library. Once inside we will move to the folder Preferences to delete the file "com.apple.systemuiserver.plist". With this closing and opening the session again everything should work perfectly.
This will leave the menu bar by default just as OS X came as standard so if we had other services anchored in it, we will have to reconfigure everything. Keep in mind that deleting this preferences file does not mean that if a program gives problems we have solved it, since if we put it back on the bar the freezes will continue, but it will help us to identify it.
More information - Migrate a user account to another Mac in different ways
Source - Cnet