Today I suddenly got this trouble. All on a sudden I can't do any thing with my iPhone. My iPhone is now Firmware 2.2.0 with Baseband version 02.28. Its unlocked and working flawlessly. I just changed the springboard theme image and iPhone becomes non-responsive.
1. Completely black screen. Nothing on the screen at all.
2. Could receive calls.( in the beginning i was able to enable while receiving calls).
3. Nothing happens on touching screen, or pushing home buttons or any other button.
4. I examined and find out i could actually shut down and restart my phone. Though nothing on-screen at all.
5. Works and shows perfect on iTunes. Works perfect in iTunes, you could Sync back or even add any song or any apps via iTunes while connected with pc.
6. Could even charge.
After all main thing is nothing in screen, absolutely nothing. The screen remains dead.
That's the sweet part. Solution is easy. Just push home button and power button simultaneously for at least 10 seconds. It will reset the phone without harming any data or setting. Now just start the phone as usual with power button. It will show Apple logo a bit longer, but it will start accurately and all problem solved.
BTW if you want to unlock your 2G or 3G iphone with latest available firmware you could use UnlockAlliPhone.com
UnlockAlliPhone.com is the best service you could find online.