You are the third person to post with this problem in a week or so. A few
things to try:
That command is called ToolsCustomizeRemoveMenuShortcut. Go into Tools |
Customize, find it under All Commands, and drag the icon to any toolbar to
access the command. If this works, check Tools | Customize, Keyboard, find
the same command, and see whether the keyboard shortcut has been reset.
If it doesn't work, it may be because something is corrupted, possibly the
Normal template or the Word preferences. If you quit Word and rename these
files, fresh copies will automatically be created when you launch Word
again. Rename rather than deleting because if it wasn't the problem, you
can copy your Prefs file back, and even if Normal was the problem, you can
copy customizations from it. Try them one at a time. The Normal template
should be in Apps | Office | Templates and the Word Prefs file should be in
~/Library/Preferences/Microsoft folder (the one in your user account).
Please post back with results, as so far no one has and there is no
confirmation on what fixes this issue, nor what might be causing it.
DM