Iphone stuck on Itunes/USB

Hi, I just tried to update my Iphone 4. Seemed to sync okay and back up the phone. But now my phone is stuck on the Itunes logo with a USB showing. Here is what I have tried:

1. following the support instructions

2. Iphone is not seen by my computer or Itunes

3. Stop/Start Apple mobile device

4 uninstall then reinstall Itunes

5. Iphone will not reboot when I hold down home/off button. Apple logo comes up briefly and then it goes back to Itunes/usb logo

This is my only phone and, well, I am kinda desperate(caregiver and concerned about someone being able to reach me for emergencies)

If anyone has any insight, I would appreciate the help. Otherwise - guess it is Apple or AT&T tomorrow:)