Are they actually missing or are they simply dimmed? If dimmed:
Is this one file in particular... One you received from a Windows user? If
so it is probably protected & you can't do anything about that unless you
have the necessary password. Depending on what version of Word & what
protection was used even a pw may do you no good.
If actually missing & this is the case in all documents -- including new
blank ones -- make sure you have Office fully updated, repair disk
permissions & restart. Should that not correct it try going to Tools>
Customize... Toolbars & Menus. Click on the name of the Menu Bar then click
the Reset button. If that doesn't restore the menu you may have a corrupt
Normal.dotm template. Follow teh directions here for testing it:
http://word.mvps.org/mac/MacWordNormal.html