For those using MX Player there is a new test version of the player available that fixes the compatibility issues with 4.4.1 and 4.4.2. The developer should have this soon in the play store, but if you can't wait, you can get it directly from his site.
In Serenity if you were using MX Player Pro, switch the external player to MX Player after you install the fixed apk, and you should be good to go again.
This link will get you the latest test build of MX Player.
https://sites.google.com/site/mxvpen/translation/test-build
