if your on a boot loop off the update to 4.4 on the nexus 7 2012 this is what i did for it to run

[jmkasperek]

got a solution for you down load the nexus root toolkit by Wugfresh he has every thing you need you will also need to download the sdk files from google these web sites helped me and ill post them here for you

this site gave me the download for the sdk How to manually update your Nexus tablet to KitKat [updated] | Android Central

this site showed me how to unlock the bootloader http://www.droid-life.com/2012/07/17/how-to-unlock-the-nexus-7-bootloader/

this site was about sideloading http://www.droid-life.com/2013/02/1...date-a-nexus-without-root-or-custom-recovery/

but this is what i used at this site i downloaded the toolkit and then after i unlocked my bootloader i used this to root and then un root to get the 4.4 kitkat his tool kit really worked if your in a boot loop off the update released

Nexus Root Toolkit v1.7.8 | WugFresh

so what you need to do is unlock your bootloader download the google sdk package follow the instruction to set it up correctly on your c drive on you pc use the tool kit to root and then use the tool kit to unroot load the 4.4 kitkat on unroot and then lock the bootloader back to stock this will get you back up and running

i do hope this helps every one for it worked for me im not taking any credit and i want to thank every person that showed me how it was done and done the right way i just wanted to help out every one else who is having the same problem

 

[Golfdriver97]

Excellent!
Thanks for sharing.

 

[jmkasperek]

your welcome i have been looking at all the problems people have been having this works on every nexus devise bad thing in the process of unlocking the boot you will in turn loose all your data so if you saved it to a sd card prior to the problem take out your d card if not im sorry but if you want you 400 500 dollor device to work again with out taking it to the carrier store for repairs this is what you will have to do