Is your iPhone dead after upgrading to 1.1.3? Read this
If after upgrading to 1.1.3 your iPhone keeps rebooting or is stuck with the Apple logo on black background try doing the following:
a) Hold the power+home button until the screen turns black. Keep holding until you see again the Apple logo (it will appear in ~5 seconds). Then, release the power button but keep holding the home button. After a few seconds you should see the iPhone is in restore mode and you can restore it using iTunes (restore it to 1.1.1, jailbreak, downgrade the baseband using the package in Installer, virginize it, restore to 1.1.2, unlock it, upgrade again to 1.1.3... this time it should work).
If a) doesn't work try the following:
b) don't connect the usb cable to your computer but connect it to power supply. Repeat the steps in a).
Let me know if someone found this tips useful.