04 August 2008
This is the problem I had (but while installing some other app)... If you run into it as well, here was the solution that worked:
"1. Boot phone 2. Hold Power + Home until the screen goes BLACK 3. Continue to hold home and let go of power 4. Plug into iTunes (screen should still be BLACK) 5. Within 20 seconds it should come up in recovery mode 6. Let go of Home and hit RESTORE in iTunes."