I bought this docking music system specifically for my ipod but the docking system keeps switching off by itself after around 15mins of my ipod playing. I checked the sleep function but it is not on. I even adjusted the sleep mode to 00. Switched on and off again but still the same things happen. What could be the cause of that and how do I fix that problem as it is very annoying. Thx (I have the manual and I tried all possible options already)