Hi, I had the same issue today. My iPhone 4S had shut down because battery wad dead, and when I connected it to the power it started to beep every 6 secs or so. I connected it to the computer and I had the same issue. iTunes was able to see it, and sync some data, but then stopped. When I removed the cable the beeping was gone. The moment I connected it to the power/computer the beeping went back again. I could see however through iTunes that it was charging, whereas when connected to the power it didn't show the charging icon. What I did is reset the phone by pressing power and the apple button continuously and then letting go. I suspect that it is the cable, because it is not in a good shape at all. Nevertheless I'm still able to use it.