I'd be curious to see a zip of your .hype document; crashing is abnormal and that is probably what should be addressed more than workarounds. Most of the time crashing happens when excessive memory is being used; while this isn't typically the case from animations, it could be depending on the audio usage. (and are you using a compressed file format like mp3 or m4a?).
As for disabling certain buttons, this could be done in JavaScript by keeping track of state. You can see a basic example here:
You could also potentially disable buttons by using the visible property to hide a button, and then potentially show a dummy one in its place.