1) The music sometimes stops playing mid-mission.
It's on my list of things to fix. Basically the sound code is just crap, so I'm rewriting it. That will all be for pre-3.7 builds though, since it will take me a few months to finally get all of that working. For now it does't just out-right crash, and that is a very big improvement from previous OS X builds.
2) When playing a MVE movie, the last interface picture keeps flickering where the black bars are supposed to be. This really gives me headaches.
Should be fixed in newer builds. I'll make sure that you get the newest build by tomorrow and you can verify that it's fixed or not.
Oh, and can someone tell how I get OSX to recognise a USB joystick ?
Don't have a clue.
It should just recognize it though, unless it isn't supported. I know that various people have had issues getting joysticks to work in OS X, but since I don't use a joystick on my Mac, I don't really have any advice to offer.