iPhone freezes 10 seconds after startup after repair

Hi,

I recently changed the back of my 3gs. it all went well and had absoluetly no problems what so ever. Got it back in one piece no problem.

Now when i start the phone up it freezes shortly after the pincode screen is reached. If i enter the pin it will freeze as soon as the last correct digit is pressed.

If i leave it locked, the swirly wheel thing eventually comes on. However this just stays on for as long as the phoene is left.

I've since updated the phone and restored it. Still the same problem.

It's not right in itunes when it's connected but it still kinda sees it as it managed to restore it. (took a few attempts.)

Another weird thing is i can use the voice command funtionallity at th epin screen. If i make it play music it'll continue to play whilst frozed???

Any ideas? Is there maybe sometihng i could leave disconnected inside to see if it's causing a problem??