1. Download JFv1.51_CRB43-US.zip (file size 36,614 kb).
2. Rename it to Update.zip and copy to the root of your SD card.
3. Shut down G1.
4. Reboot G1 by holding down Power+Home buttons at the same time, which should bring up the bootloader.
5. Bring out the key board, first Alt+L to display log, then Alt+S to apply patch; this should apply the update.
6. Once done, G1 prompts you to reboot.
7. Per my personal experience, I got stuck on the Android logo (the 3D chrome logo), which froze at the animation loop. What I did was a) Took out the battery and reboot, which doesn’t seem to fix the problem; b) Reboot the second time by going to 3, 4 again. On the bootloader screen, Alt+W to wipe data and reset to factory default.
8. Power up G1 once done. That’s it.
At least it worked for me:)
