iPhone Audio Playback

We have 3 iPhones for testing.  Two of them play the modern player course with audio.  

Worth mentioning here, the player skin does not show an audio control on the iPhone but it does on desktop.

The third iPhone will play audio on YouTube or Safari web pages, but it will not play SL's Modern Player audio. So this isn't a volume control issue.

This is why I mentioned there is no volume control in the player skin.  Should there be? Can we force one?

Does anyone have experience with this? Anything we are overlooking?

Sam