I am experiencing an interminnent fault with my entire audio system. I have a 05 STS that muted in the middle of my drive last week. The screen shows the CD playing and navigation works but no sound. I even noticed that I don't hear the turn signal ticking. The settings menu doesn't allow me to change vehicle settings. It displays a "vehicle personalization system error". Before I could get it to the dealership it somehow began to work just fine for a few days but now it's out again. Does anybody have any idea what could cause this error?