Hi
Just wondering if you accidentally "pinched" the power button board cable near the hinge area when you reinstalled the display.
Here is a link to the [http://downloads.dell.com/manuals/all-products/esuprt_laptop/esuprt_studio_laptop/studio-1737_service%20manual_en-us.pdf|service manual] for your laptop.
Here is an image taken from the service manual to show where I mean.
[image|1323105]
(click on image to enlarge for better viewing)