Hi,
I have a built in nav in my car so I don't use the 5800's ovi nav in anger much. Still I want to be fluent with it so I can use it when needed. It bothered me that despite installing language files it would not talk to me in the car. It finally occured to me that I have Handsfree Link which connects to the phone with bluetooth. Handsfree Link isn't like a headset, it only transmits audio while in a call. Still the 5800 sends all audio to the BT device, resulting in silence 😊
I'll send an email to Nokia to see if they have any suggestions. I'm afraid they'll say "you're out of luck".