One, it needs a clear view of the sky not just directly above but also around the car. This happens me sometimes when the car is downtown and the only clear view is directly straight up. or after going around inside a parking garage.


Two you may have a issue with the antenna.

 

I was trying to replace it with the new one. No result. And I have this issue for few months, it was good sunny days during this period and no success.
I consider that no altitude meaning could lead to the problem.

 

I had to go to San Francisco last weekend and my Navigation is crap. The arrow was showing me couple of blocks away from a real location! My portable Garmin is way better then the $1700 BMW navigation. Come on BMW work with Garmin and put them in the US cars. Let the Navtaq do the honor in Europe!

 

hold volume and press both eject buttons WITHOUT DVD in the reader and let the drive reboot.
If this doesn't help make sure that the blue fakra on the back of the CCC is seated correctly.
Make sure the blue fakra on the sharkfin is connected correctly.
IF you have a retrofit the cable may be pieced together with fakra connectors. or you may have a crimped cable.
Trace it out. to see if the problem is with antennae (which I suspect) buy an after market one for testing and keep the antennae about 12 inches away from the CCC. Wait about 15 minutes for the signal to propagate.
Not a DVD issue IMO.

I had the same issue after a retrofit some years back and found that i had not completed the connection to the sharkfin. Was difficult to pin down at the time but now just seems common sense.
Goodluck