I've had the same bug happen to me 7-9 times since I've owned my 5N since November. I always manually set my focus to DMF and then purposely select another option in the menu so it that "autofocus" isn't remembered as the last menu choice. Then for some odd reason once in a while, it will change from DMF to AUTO by itself. This has happened on firmware 1.00 and 1.01. I usually shoot in AV mode 95% of the time and always leave it on DMF. I think it's a glitch but I can't reproduce the issue on command...it's very random.