I am using the Menubutton to provide an accelerator effect via the
underline option.

When I import the basic widget via from tkinter import * the widget
performs as expected (F_ile) is activated on pressing Alt+F and the menu
is presented.

Conversely when using the ttk widget via "from tkinter.ttk import *" the
Alt+F key combination does not activate the Menubutton widget. In
addition to this pressing F10 does not activate the menubar.

This is on Ubuntu Karmic, Python 3.1.1+ (r311:74480, Nov  2 2009,
14:49:22) [GCC 4.4.1] on linux2

By commenting out the import of the Menubutton at the top of the script
you can hopefully see the behaviour I have described. This
ApplicationMenu class is called in another script (self.root.MenuBar =
ApplicationMenu(self.root)).