Same thing here and @ssmckee hit the nail on the head with the problem…
The issue is that another company has produced a theme called Prose. WordPress sees that I have the Prose Child theme on my site and thinks I need to update to the new “Prose”. I don’t because it’s actually not the Studiopress Genesis Framework Prose theme.
BTW: if you have the latest version of Prose (v.1.5.2) from StudioPress, this is a non-issue. It seems to happen when you have v1.0 of Prose
