Originally Posted by ryderbg
I just locked the bootloader. I used the command fastboot oem lock and there is no padlock now. Also Lock state changed to locked. I think now I can return the tablet in the shop.
heres a funny story but what it resulted in and how i fixed it seem to apply to the problem you have.
i have a cracked screen on my nexus and it was registering a touch at intermittent intervals making the device unusable. i posted in here about the same time you did for help. while i was waiting to see if anyone knew if i could just disconnect the screen and use a bluetooth mouse with a hdmi adapter (slimport not mhl, thanks meekrawb) i connected a usb mouse with an otg cable. the mouse worked but i couldnt see how to turn off touch screen as an imput. as kitkat has been release and i hadnt updated i thought i would give it a try and see if that would reset the screen and stop the touch. It downloaded the update and when it rebooted it opened up a mod recovery screen (i forgot that i had rooted it). it asked me to slide a bar on the bootloader screen to continue. The usb mouse cursor was not present on this screen and the touch screen doesnt work so i couldnt get past it. i turned the device off and on again (what else do you do when your stuck) and it would open the google screen with the unlocked padlock but then just stay on a completely black screen. same as yours. I connected it to the computer and it recognised it. i opened wugfresh's root tool kit (old apple jb's sometimes had recovery abilities built into them so i thought this may aswell) i clicked on flash stock and unroot with the radial button on soft bricked and followed the instructions. now my device is unbricked and even the touch has stopped. Happy days hey. you'll need to unlock your boot loader again but its worth a try before going to the store, you can always lock the bootloader again if it doesnt work.
i know it didnt need all this to say "connect it to the root tool kit and try that" but i thought you would enjoy a laugh