Seems like Patchou forgot the change the version number internally. The file you download (either through auto-update or from the site) at this moment
is a new version, because it was digitally signed yesterday (17th). And like you said setup shows as build 380, but not in the about box (where it still says 378).
I see the changelog is changed now too:
http://www.msgpluslive.net/download/changelog/