You can certainly use two sources at the same time but you also need to check the settings are correct: Settings > Bluetooth and then enable both 'Phone,Navigation' and 'Media' when you've paired correctly. If i'm understanding your problem, it's i think that the TourGuide is meant to be delivered by the the second source [Media] which won't work unless it's also enabled. From memory it's not enabled by default whereas the first is.

Post again with more info if the above isn't what you need.