We don't know what happened. First, the concept of energy became meaningless in the sense that we can only calculate the energy of a system by reference to its properties in an asymptotically flat space-time. There is no conserved energy parameter for a system in a badly curved spacetime such as the one at the Big Bang. Heisenberg's Uncertainty Principle, translated into a hypothetical quantum theory of spacetime would be recast to state that you cannot specify the exact geometry of space-time for a specific parametrization of space-time in terms of time-like or space-like variables. This is the essence of what is called 'quantum cosmology' and the idea that time and space become meaningless parameters at this state. Cosmologists then talk about 'sums over space-time topologies' and 'sums over universes' to unravel what is going on. Heisenberg's Uncertainty Principle isn't violated in so much as it is superceded by a new formulation of it in terms of the quantum features of the universe that are now present to work with.