If you turn off "Fade" desktop effect the menus and all kind of popups sometimes drawn incompletely. Sometimes does not drawn at all.
The incomplete drawn menus work, so if you move the mouse over the undrawn items they are updated and drawn correctly then. 

It does not happens without compositing.

I see this very annoying bug from Ubuntu Precise (KDE 4.8.2). It does present in Ubuntu Quantal (KDE 4.9) so far. It was OK in Ubuntu Oneiric (KDE 4.7.4).

It seems that it is hardware independent, it happens with (nvidia, nouveau, intel X3000). VSync, compositing type settings seems does not effect.

I know only one workaround: turn the "Fade" effect on and set the animation speed to "Very fast". Which runs the other preferred animations too fast.

I remember seeing this bug in the compiz buglist which is fixed since then (sorry I could not find the link).

Reproducible: Sometimes

Steps to Reproduce:
1. Ensure desktop effects are enabled
2. Turn off "Fade" effect
3. Pick an application with lot of menus items, my favourite is Krusader
4. Make it fullscreen (it might happens more frequent on bigger windows)
5. Move the mouse over the menu bar and check if every menu pops up right way
5b. right click to open local popup menu
Actual Results:  
Some parts of the submenus will be missing, often more than one rectangular area.

Expected Results:  
Proper submenu / popup drawing.