You need put the iPhone in DFU mode.
Try this steps:
1. Click at same time in power buton and home buton, until appears de apple logo;
2. when the apple logo appears release the power buton but continue old on the home buton until the itunes open.
3. after that the itunes send this message "iTunes has detected and iPhone in recovery mode. You mest restore ...".
4. Click in the OK buton;
5. Clck int the iTunes Restore buton. The iTunes was restore the iPhone setting to the original firmware;
6. After that Run the aplicattion iJailBreak 0.5.3. The link is
http://ijailbreak.com/. This aplication is for MAC.
This aplication put your iPhone 100% well. This jailbrack ou jailbreack and unlock. After 3 minutes the iPhone is fine, with 1.1.3 firmware
Tell me anything.
If you cannot run your iPhone in DFU mode. verify the energy in the iPhone or verify the connetion (cable) from iPhone to USB socket.