Three years ago I purchased a 2005 Q45.
About a year ago, I first noticed all the windows down when I left the house for work. I chalked it up to keeping the key in my pocket and moving about, so I began taking my key from my pocket most of the time (also I keep house keys, etc. on another key ring). It happened again, with the keys on the dresser, during a thunderstorm. On the windy side, the inside door handle filled with water and the rear seat reclined. The water-logged switch wouldn't work, so I paid the dealer to disconnect the switch and leave the seat upright, no longer functional. He said I needed a new 12v battery also, that when the battery starts to die, the computer spasms and that probably caused the windows to go down, so I got a new battery. About a month later, windows down again AND I had to turn ignition several times to start the car. Dealer put in new battery in key. No charge, after all the other. That was about a year ago and the windows self-rolled down only once, but occasionally, when I turn the key - nothing. I turn it again and the starter works without hesitation. Maybe the battery fixed it. My wife won't use the car and teases me each time I have to turn the key more than once. It will soon be a year with new 12v battery and 3v battery and the windows have not self-rolled down, but I wonder.