Same here. I tried changing the "timeout" to never, but it didn't make a difference.
Netflix keeps the screen up indefinitely.
So does YouTube.
I don't know what Navigation's problem is yet.
btw, my motorola micro-usb car charger doesn't seem to work with the DNA. It shows charging, but even after a 3 hour trip (most of the time screen off) it never went up. Even worse, when it was on the car charger it schizophrenically kept trying to got into "dock mode", even if the phone was just sitting on my leg. Weird.