I just fixed this..
First install this
sudo apt-get install gconf-editor
Then open it
gconf-editor
Now click onapps then metacity then click general
button_
A dialog will open in the right of the window, now find the option button_layout and change the text next to it to close,minimize,maximize and this will fix it.
Also you can change the button order (eg minimize,maximize,close) if you wish.
Or add a drop down menu by doing this to put it in the right corner minimize,maximize,close:menu or menu:minimize,maximize,close for a left menu with buttons on the right.