The problem was stemming from the Renderer. I solved it by switching off GPU-accelerationAccording to Adobe, it's a bug. I thinkUntil Adobe fixes this means I'm no longer using my GPUbug with an update, whichthe workaround is a power tradeoff. Hopefully I'll be able to switch back once I'm running a non-beta version of Mac OS Xswitch off GPU acceleration in Project Settings.