You are using GNU emacs aren't you? I don't see why the binding should be any different (unless its an old version or something). Try starting emacs with the -q argument, it will ignore all customizations in .emacs and start with the default settings.
Also try
M-x describe-function RET tmm-menubar and see if a binding is mentioned in line 2. Mine says this:
Code:
tmm-menubar is an interactive compiled Lisp function in `tmm.el'.
It is bound to M-`.
(tmm-menubar &optional x-position)
Text-mode emulation of looking and choosing from a menubar.
See the documentation for `tmm-prompt'.
x-position, if non-nil, specifies a horizontal position within the menu bar;
we make that menu bar item (the one at that position) the default choice.
[back]
Also try
M-x where-is RET tmm-menubar, it should show you what key it is bound to.