1. Connect your 3GS to your Mac and put it into DFU mode.
2. On your Mac, click the Apple Logo in the upper left corner.
3. Click About this Mac - More info...
4. Click Hardware - USB - USB High Speed Bus - Apple Mobile Device (DFU mode)
5. Look for the iBoot version under the Serial Number.
6. If the iBoot version is 359.3.2 or higher, you have the new one that can't be JBed (yet)
Bummer! Bootloader 359.3.x hasn't been able to be jailbroken for a while now on 3GS models. Any one have any best guess as to when it may be jailbroken? I was hoping to sell my iPhone 3GS that is only a month old jailbroken and hopefully unlocked as the funds would be used to purchase the iPhone 4.
Thanks! Happy jailbreaking!