a likely cause is trouble with handles in your menus (where on top of the standard ones you have options like "scan this with ***", "undelete with ***", "share through ***", "burn this with ***" where *** = some software), do you have any fancy extensions like that? If that is so then the program ShellExView might help you out
other than that, what type of windows do you have? can you regain control through your task manager or is it a full fledged freeze?
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