Windows Phone 8.1 issue: "Completing the update" has locked up Music app

For those of you running Windows Phone 8.1 (Developer Preview)...

About two weeks ago, my Music app started installing an update. I received a "Completing the update" message and since then, the app has been locked up and unusable.


There's nothing I can do to change, quit or restart this process, so I'm stumped as to what to do.

Any suggestions or insights?