If you've downloaded the latest iPhone firmware on to your previously unlocked iPhone, you have a course of action available to you that will unlock all your iPhone's functionality except for your phone service.
The ticket is iNDependence, a Cocoa-based app for Mac OS X. This provides a UI for modifying your iPhone.
You can download it here. I guess that would be the first step.
- Make sure you have a copy of the 1.0.2 firmware handy in ipsw and decrypted form.
- Reboot iPhone holding top (power) and home buttons *BUT* release the top button 10 seconds into it (right after the screen goes dark).
- The iPhone screen will appear to be off, but start iTunes (latest version worked for me on the Mac).
- Option+Click restore and select the 1.0.2 firmware ips.
- The phone will restart and error out at the end with an unknown error 1013, this is expected.
- Restart iTunes and let it get to the screen that says you have an invalid SIM
- Launch the latest iNDpendence
- Jailbreak the phone using a decrypted 1.0.2 (it will flash all sorts of error, but stick with it)
- Activate the phone
- It will show the SIM error but you should be able to get back in.
Additional stuff for code jocks here.