Recently, the factory radio in my 2007 Altima has started going out unexpectedly. It will work and sound will come from the speakers at times, then the sound disappears completely. When this happens, I notice the "ST" is not showing on the display and I can't adjust the volumn at all. At times, the radio will start working again, then will go out again. The radio still has power to it, but can't hear any stations, play a CD, or use the AUX jack to play music. All fuses appear to be good and intact. Don't know what the problem is...can anybody help? Also, if I have to replace the radio, can I replace it with another factory radio from another 2007 Altima without having to take it to a dealer to get any potential security (anti-theft) code reset? Any and all help is appreciated. Please and thank you!