Comment 5 for bug 688811

http://library.gnome.org/devel/hig-book/stable/windows-progress.html.en
"If progress of a task makes a window temporarily unusable, do not present a modal dialog-like progress window in front of it. Instead, present progress somewhere in the original window, making all its other elements temporarily insensitive. This helps reduce visual clutter."

i think that is the greater violation, fixing that would make this bug report obsolete.