Popup menus appearing behind windows

I have just installed openSUSE 11.1 with GNOME, and I am noticing a very strange behavior. When I right-click on certain things, a pop-up menu sometimes appears behind the window, where I can’t see most of it.

For example, when I click the “Computer” button in the lower left-hand corner of the screen, an application menu appears. When I right-click on one of the “favorite apps”, the lower edge of the pop-up menu appears below the bottom of the window. I now have no way of removing items from the “favorite apps” window because I cannot see the command to remove the item.

Has anyone every seen this behavior before? It is most annoying.

One additional observation: I can work around the problem by globally disabling desktop effects.
(Applications > Utilities > Desktop Effects)