When setting a window/dialog title to an empty string, Compiz changes it to "untitled window". This goes against the GNOME interface guidelines, which state that alert dialogs are supposed to have blank titles: http://developer.gnome.org/projects/gup/hig/2.0/windows-alert.html Of course a workaround is to use a string with a space, for example, but this is far from ideal because most existing applications use empty strings as usual.
This was fixed some time ago. You need a version of libwnck that has wnck_window_has_name, without that gwd can't properly determine if a window has a name or not. If compiz is built agains a version of libwnck that has wnck_window_has_name, it should work fine.
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