So I have now been able to solve this for myself through a couple of steps... not sure which (or both) actually fixed it, but it's worth a try if you're still having issues.
- do a soft-boot on your iPhone... (holding down home and power button until it reboots)
- make sure the iDrive has the latest update
http://www.bmw.com/com/en/owners/nav...update_vin.jsp
Good luck!