Yesterday I installed the new Gold release, and I found that the models I exported to AS from Frefab3D 2 had problems compiling: they searched for DefaultBitmapData, that is not in the Gold release. I fixed the problem by taking this lib from the previous release of Away3D.
I should try to re-export the models with the new Prefab3D version, but I have no time now: does this fix the problem?