Not sure how to explain this but the situtation is as follows.
Sometimes an application will throw a popup or a contextmenu. Then after I close that popup or menu and switch to a different application or workspace there is still an echo, a grey area where the popup or menu was. The only way to get rid of it is either to reproduce the graphical effect and hope it goes away properly this time or to close the owner of said popup or menu(so if Chrome made a popup and it leaves an echo it will only go away after closing all instance of Google Chrome).
Does anyone have a solution? I tried Googling but it's hard to Google for this sort of thing(that or my Google-fu is lacking).
I use Ubuntu 10.10 and Gnome 2.32.0.
I included a screenshot. The effect is in the lower right corner.