When a copying process window is active (has focus), the "Cancel" button inside it shouldn't have focus by default. This could prevent accidentally activating "Cancel" (eg with keyboard Enter, or Space key) when you think another window has focus (some window manager themes do not make it very clear...). This is even more a problem considering bug 4263 , as you have no easy way to resume the copying process (no "skip all" button). Maybe it would be good to give focus to a "dummy" item (progress bar, label...) by default. I hope to see this corrected. Thanks a lot :)
Fixed in 406b914.