I have this issue now. I'll have to try what you did.
K. This is what worked for me, step by step.
Notes: this is just for a north american, ATT branded 920!
Do not plug in your phone until told to do so!
I'm just helping here, relaying what worked for me. If this bricks/messes up your phone even harder, i apologize but you're doing this at your own risk.
Read through everything once, before proceeding.
1. Left the phone plugged in for a little while so it had some charge to it.
2. Went to this post:
http://forums.windowscentral.com/no...h-any-lumia-920-full-amber-gdr2-features.html and grabbed this guy's nokia care suite from his skydrive. If you try to use the one from the main unbricking sticky post at the top of this forum, the care suite won't download the firmware and navifirm 1.7 doesn't work anymore.
3. Once you have the NCS (nokia care suite) from juan6996's skydrive, install it.
4. Open up the care suite and choose "product support tool for store"
5. On the following "Sign In" popup choose "Care Suite External" from the "Sign in to:" dropdown
6. Click "Sign in"
7. Once the product support tool opens up, from the menubar at the top go to Tools --> Firmware download
8. You'll see another window popup asking for a product code. The product code for an ATT black lumia 920 is: 059L848 Enter it and click on "Check online"
Note that there are product codes for each color variant. You'll have to google the other colors if necessary.
9.Click on "download" once the firmware comes up. It will say something about it being queued for DL. You can now close this window via the red "x" in the corner.
10. Let it download. It took me about 30mins.
11. Once the firmware has downloaded, go to File-->Open Product and filter for RM-820, only one should come up. Click on "Open"
12. Now go down to the lower left hand corner where it says "Programming" and choose "Recovery"
13. Click "Start"
14. It'll act like its re-downloading the firmware but just give it a minute.
15. At this point have the phone ready to plug into the computer but don't do it yet.
16. It'll then detect that the phone isn't plugged in, and show you a window to that effect.
17. At this point, if you can turn the phone off, do so. If you're stuck then soft reset. As soon as you feel the phone do its reboot click, plug it into the computer and click "Retry" on the window.
18. It should begin flashing the firmware. Mine took about 5-10mins since its basically a factory reset and isn't keeping anything.
19. Once its done it will reboot on its own and drop you into the setup your phone screen as if it were a new device.
Note: In order to get your backups back (the phone should have made one last backup before the first update to Amber that got you stuck in the first place) sign into your MS account BEFORE setting up your wifi. Also remember that if you have 2-step verification on you have to generate an app password for your MS account to sign in on the phone rather than the password you use to sign in normally to check your email, log into your PC, etc.
*this post not edited for spelling for expediency's sake.