When did the Angels fall??

Kabbalah teach's that much went on in the Spiritual worlds
before any corporeal creation came into existance. But all that went on was just in an instant, as time didn't exist until corporeality. That instant was the cause of the big bang, when the creature fell from a unity with the Creator, in an unconcious way, like a baby in the womb, to a state of complete oppositeness, called this world, through the development of conciousness and desire.
The fall happened before the creation of this world, and this world is the result of it.
http://www.kabbalah.info/engkab/kabbalah-video-clips/kabbalah-revealed-introduction-to-the-four-phases-of-direct-light
Maybe this video will explain things a bit better.