Happens on my phone as well as on my eReader, so it should be indifferent of android version.
I would guess that in english the buttons are labelled "Cancel" and "Abort"? Both could be translated as "Abbrechen".
I've noticed that on my cell phone the buttons have different colors (though that doesn't solve the problem, blue and red - a nice touch, but there is no universal color scheme for such a situation, I think?), but on my eReader it's of course gray in both buttons.
Perhaps it would be possible to add icons? A checkmark for "Yes, stop the WU" and a cross for "No, don't stop it"?
Christoph