Menus not Displaying Properly

My problem is that not all of the main menus are displaying. In particular, the Insert, DHTML, and Table menus are completely missing--the menu name doesn't even show up in the toolbar, so there's nothing to click. My customized menus are also missing. The only time I can see them is when I am in the Customize window--as soon as I close out of it, they all completely disappear again.

In troubleshooting this, so far I've tried:

• Right-click toolbar area > Customize > Select Options > Always Show Full Toolbars > Close. As soon as I click close, the menus disappear again.
  
• Customize > Commands > New Menu. Create a customized menu called InsertThis and manually add the same commands to it that are in the Insert menu. As soon as I click close, the menus (including the new, customized menu), completely disappear. (So apparently customized menus also won't display.)
  
• Customize > Commands > add various menu commands to the toolbars. Close. They stay there, visible, no problem. (So apparently only the menus are affected--not the toolbars.)
• Restart RoboHelp. No change.
• Restart computer. No change.

Anybody have an idea why these menus aren't displaying properly?