Avier + XC Soar frozen screen

I purchased a Avier and installed XC Soar. When I use it to fly cross country, it freezes up after less than an hour of use. I see the course line and the glider symbol. but it doesn't move. I can't get the "quit" message to show up.

The first time it occurred I was flying my Duo with another pilot, so I spent about 20 minutes working to get it to shut down and then restated it. Sat. I was alone in the Duo when it happened. All I could do was shut off the Avier since I could not get a "quit" to shut down the program. After following roads for a while, I was able to get it back. I did not use the Avier for the first leg of the trip, since I have not installed a plug for it. It failed after about 15 minutes. I was not touching the screen, and it was in its cradle.

What is happening to cause this serious problem?