I did an unlock and jailbreak for my friends 3GS running 3.0 and everything was working fine. He then decided to "Erase All Content and Settings" from the iPhone settings app.
Now when you turn the phone on it stays on the Pwnage Pineapple Icon.....Pwnage or iTunes doesn't even recognize it. I even tried to follow the DFU instructions from Pwange, still unrecognized???
If I hold the power and home button to restart the iphone the Pwnage Icon appears again.....even after 30 mins or so the icon is still displayed.
You are going to have to restore. Force into recovery mode by holding down home and power until you see the connect to itunes logo (or the steve jobs cartoon). Then plug into iTunes and hit restore. You will then use blackra1n to jailbreak and unlock (if needed).