emacs -Q
 
C-h i
 
Pick a manual, and go to any node that has a menu too long to be
displayed completely.
 
Menu links seem to cause a blue strike-through line in the mode
line. It seems that a menu link directly underneath the mode line
(hence not visible) has its underline brought forward on top of the
mode line.
 
C-l removes the strike-through display artifact. Otherwise, it
persists even if you move to a node that has no menu or has a menu
that can be displayed completely.
 
After clearing the screen this way, if you go to a node with a menu
that can all be displayed, and then you manually shorten the frame so
a menu item is hidden by the mode line, then the strike-through
returns.
 
See attached screen shots.
 
In GNU Emacs 23.0.60.1 (i386-mingw-nt5.1.2600)
 of 2008-11-24 on LENNART-69DE564
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4) --no-opt --cflags -Ic:/g/include
-fno-crossjumping'