When you installed iOS 7, was it the GM?
what do you mean GM? well my iphone model is A1428 unlocked so yes i think it is GSM.
If you hold the power and home button for 20 or so seconds what does it do? Apple logo and then black? If so how long does the apple logo stay up.
that is NOT DFU mode! we have been trying to tell you this.when it turns on it funny cause my screen is white with apple logo black and it stays for like 3 sec and then turns into DFU mode where it shows the cable to plug in the itunes....helpppp
I could be wrong, but, you shouldn't get that message, as others are saying here, it seems you are not in DFU mode
...connect to your mac, then put the phone in DFU mode (follow the method in this vid, below), when it pops up to restore, click ok, then use option key to click on restore and select the iOS 6.1.4 .ipsw. This is assuming you have 6.1.4 from a previous update through iTunes, if not, you need to make sure you are using the correct .ipsw for your version of iPhone 5 (GSM or CDMA).
Try again using this method: http://youtu.be/2pGYzSXn3Bw?t=1m24s ...if you are not sure if you have the correct .ipsw for your device, go back to the beginning of the vid.
you've gotta be trolling us..
that is NOT DFU mode! we have been trying to tell you this.
Take a deep breath, slow down, chill, check out my previous comment and watch the youtube video link posted.
That's what we keep telling you. That isn't DFU mode. Follow the instructions to go into DFU mode. DFU is a totally black screen with nothing on it. The only way u even know u are in it is that iTunes will come up with a connected phone. And your computer will show it too
When you installed iOS 7, was it the GM?
You have the wrong firmware then. If you are really in DFU and it gives you that error you need to download the firmware again. And have you fixed your host file too?
Tiny umbrella will modify your host file. Google how to edit your host file to fix error 3194 and error 21 for a Mac.