I have also experienced this problem with my Vista HCx using alkaline batteries 3 times. Once the unit had been sitting in the cold car (~30F) and it took two restarts to return to normal operation. Twice the unit was in my pocket and fairly warm. The car was about 30 F, but I started the unit fairly quickly, so it shouldn’t have cooled much. These two situations only required a single restart. I have only seen this problem in cool air.
I'm glad to see I'm not the only one. I will also report my problem to Garmin.
