Same problem iphone wont boot and itunes wont restore
I have a 3g and had the same problem after trying to install something from Sydia. No matter what itunes would not restore and give me an error. Then the iphone screen would go black and I would have to hold the home and top button for the phone to come back on but it would still show only just the apple logo.
I tried to reinstall like 12 times then one timeout of nowhere, not sure If it was a different sequence of holding down the buttons or some just some random thing but instead of showing the apple logo I got a screen showing the iphone cord and the itunes logo. Then I tried to restore again and it worked. My suggestion would be to just keep trying to restore putting your phone in DFU mode. I know it sounds stupid but that's what worked on my phone.