I'm having the exact same situation, I have Nokia Lumia 520 and stop working when I replaced the glass (digitizer) no LCD screen. The just won't turn on, it just gets to the Nokia logo and then reboots infinitely and never gets to turn on.
Have you found a solution yet? If so please email me at garrofederico@hotmail.com
Is there any chance that the phone is not working because of the new digitizer chip is not compatible with the phone?