I Did it on my iMac G4 Running 10.4.11, and it completed, but didnt actually Jailbreak my iPhone, it would say its finished, and that the iPhone would reboot itself, then it would appear turned off, i went for a shower, came back 30 mins later, still a black screen, no backlight, so i turned it on, and nothing, no Cydia, no Installer.
Tried it twice, no success 🙁