I had this same problem when I first got my phone (about a month ago) and tried to use the NSU to update the FW. If you look at the screen closely I think you'll see the Nokia sign (which is initially on a white screen, but then on a grey one) disappear. That's about the same time the buzz happens. I think it's basically the phone switching off and then it starts up again trying to boot and the cycle repeats.

Some people recommended charging the battery in another phone, which I did, but that changed nothing. In the end I was able to flash via USB (Windows XP). I realise you've already tried this and it didn't even work, so not sure what to suggest. I just wanted to say that I don't think your phone/battery is charging in the current state it's in.