Users of the newer Office 2007, 2010, and 2013 versions have noticed strange line overlays in the Menu (book). There are two possible solutions to this situation:
Solution #1 (Easy Difficulty):
Solution #2 (Medium Difficulty):
Another way to fix this problem is simply to remove the lines that are causing the display problem. To do this, open the mnuMainMenu form in design view. Click on the box surrounding the “book”. Once only that box is highlighted, hit the delete key.
Then, for both the left and right sides, select the rectangle behind the tabs. When only that box is highlighted, hit the delete key to delete those boxes.
When complete, the menu system in normal view mode appears without the intersecting lines. The remaining vertical lines behind the tabs may also be removed to further clean the menu interface.