iPhone 4 Battery not charging after screen repair

Hi

I recently replaced my front screen and back cover. All went well except that after completing this (slowly and carefully), the phone would no longer charge. I could plug it into the mains charger and it would start up and get to the grey screen with iPhone written on it.

When I opened the slider, it would show me the iTunes screen.

The issue is that there's no way to connect it to the Mac, because as soon as I unplug it, the phone goes dead.

If I keep it plugged to the mains, it just loops and restarts after a while.

The screen stays on the apple logo for quite a while, then I get the "new phone" screen.

I thought that maybe my battery was also dead, so I ordered a new one. The same happens except that I can actually connect it to the mac and the apple logo shows up (with the old battery it wouldn't).

With this new possibility, I tried to restore it. I can get it to recovery mode and I get as far as iTunes extracting software, verifying the phone with Apple, preparing the phone(dim screen light comes on) and it seems as if it is then restoring the phone but then iTunes gives and error message (2001) and quits the restore and the screen goes back to the apple logo.

Any help would be much appreciated.

Thanks

Gianni