Just today I started having a problem with my Desire HD. I've had it for about a year with no dramas at all till now.
I agreed to update the navigation app and I got a warning about a 30 day free license for premium navigation/maps.
Now the navigation app will open completely on its own after anywhere from 1 second to maybe 30 seconds at most, of the phone being idle
When it opens, it will show the navigation menu (destination/phone/get more/mute etc etc).
The app is ALWAYS showing that it is "searching for GPS" in the top right corner.
If I turn GPS satellites OFF, the app will open with a window stating "GPS satellites must be enabled to use location service" and I can only choose "Settings" or "Cancel". Choosing cancel will take me back to my home screen, but it doesn't change the fact that the app will open again in a number of seconds.
If I choose Settings and turn GPS Satellites ON, it takes me straight back to the app and the navigation app menu where the app is still 'searching for GPS' in the background.
I can choose 'Exit' from the navigation menu, but the app will re-open itself automatically in a small amount of time again