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Why are you driving around with your test device? Shouldn't you just be using your primary device in the car?

That's how this is tested! By driving around..

Besides many of us use our primary for the betas, such as myself, and rather enjoy it! :)

Google Maps just updated yesterday, I use Navigon also (works since beta 3) - so I'm not dependent on Apple Maps - but I certainly want to see it working.

Others using beta 3 with iPhone 5 AT&T seem to have it working, so trying to figure out what's different can be helpful...
 
You can "fix" this in B3 by pinching and zooming the screen. It will return as an issue the next time you use maps. I am a developer and I have filed a bug report with Apple.
 
I have experienced the same, but navigation resumes properly (Siri talking me through the route, etc).

I've assumed it is simply beta wonkiness.
 
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