I had several similar problems with my PSR-800, one of which is it would freeze and I would have to remove the batteries and then put them back in to get it to work again. I eventually traced the problem to a poor connection. I replaced the the cigarette lighter adapter and the cable and my problems have since gone away. Apparently when using it in an auto it becomes very sensitive to power interruptions. I noticed that sometimes when I'd hit even a small bump in the road the cable would twist and momentarily disconnect the scanner. Every time this happened, something would happen to my scanner.
Hope this helps.