Try to restore it from DFU mode as follows:
- Reboot your computer
- Disable your antivirus and firewall
- Connect the USB cable to a USB port directly on your computer, not a hub - do not connect the other end of the cable yet
- Launch iTunes, making sure you have the latest version (11), or at least 10.7
- Hold the HOME and SLEEP buttons on your iPhone for EXACTLY 10 seconds, until the screen goes black, then release the SLEEP button but continue holding the HOME button - If an Apple logo appears you have held too long; do it again
- Connect the cable to the phone while holding HOME
- iTunes should recognize a phone in Recovery mode. When it does release the HOME button and wait
- Don't touch your computer or phone until the restore completes or you get an error message; ignore any other displays or messages on the phone.
If you get an error message post it for analysis. Include the error number.
My phone is not jailbroken. I ended up having a friend try to restore the phone from his Mac (I have a PC), and all he needed to do was plug it in and it came back, without the software update. I think I'll NEVER update the software again from my PC. This is the second time this has happened to me with a software update I've done on my PC, but at least the last time it was still under warranty. I think all software updates from this point forward will be made via iCloud. I've not had a problem doing this before. Thank you for your advice.