The ribbon cable has most likely become detached causing the screen to go black during a call, your camera to not work, and/or the sensors to not work.
This link below shows the cause.
Symtoms will be:
1. Camera does not work
2. Green/orange led charge light does not work
3. Ambient light sensor does not work
4. Phone goes blank during calls and cannot be fixed without pulling battery
Cause:
The first ribbon cable of the logic board is unhooked/latched
http://android.googlecode.com/issues/attachment?aid=152910108000&name=Help.jpg&token=lScixdbRVdAnN0g5MNOb885fjEg%3A1330029264192&inline=1