I recently bought a boss 754di radio and I was wondering why the USB only charges my iPhone 4s for about 30 seconds and then shows erra. After it shows erra it goes to the radio function by its self. And another issue I'm having is its not recognizing the SD card that has my music on it. There's music on it because I use the same card in another electronic that I have. Please help me with these issues. Thx