I have unlocked 2 different iPhones using iPlus 2.0b three times without any problem.

But then came the third iPhone, always fail. Used 3 different PCs, including one on Windows Vista. The carrier option is always missing.

But then I downloaded Ziphone 3.0 (just released), and used it to unlock, and it was finally successful.

What I'm trying to say is, different iPhone will need different application to unlock. Just try both Ziphone and iPlus. One of them will work.