Hiya! I recently got an iPhone second hand. Because it's second hand, it didn't come with the cable in the original box. It came with a Universal Dock. It's not an Apple Universal Dock, (at least I don't think so, since the images i Googled up of that weren't the same as what mine looked like). When i plug this dock into the wall socket, a window comes up on my iPhone display saying "this accessory is not made to work with the iPhone". Despite that, it still charges fine.
So today, I decided to try syncing my secondhand iPhone to my iTunes Library. The first few times, my iPhone didn't even show up in my iTunes at all, so I unplugged it several times. Finally, when it showed up, I clicked update software under the Summary tab, and it started downloading. When it finished downloading, some window on my Macbook popped up and said that some error had occurred. Then I got the picture of an Apple USB cable and an arrow pointing upwards to the iTunes logo on my iPhone LCD. And it's been stuck on that ever since.
I've tried charging my iPhone, Switching it off and on, and unplugging my dock from the laptop. The image doesn't go away. So i can't even access the home menu on the iPhone. I tried clicking the restore button in my iTunes, but it just said an unknown error occurred (2005), and my iPhone disappeared from the Devices list...
You need to get the cable that came with the iPhone or a proper cable & stop using that dock. Also, make sure its plugged directly connected to a high speed USB 2 port. That's the source of your problem.