I had the same problem. I just fixed my phone. You have to hold the power and home button down until it shuts off. Then hold the home button for about 3 secs and then connect it to your computer. It should then ask to connect to itunes, or it will automatically connect. from there, you can restore your software.
if you have mac osx, there are other methods of restoring it, but i have windows and had no other choice but to do this.
i hope this helps you as it did me.