This is driving me round the bend! I am working with Unity 4.6 on a Mac. When I try to move folders within the project view which contain a lot of assets such as textures etc, Unity decides to hang/crash and then when I reopen unity it starts to import all the assets in the folder I tried to move. This has happened to me many times, and import times are very long. Does Unity really reimport all the assets each time I move them in the project view?!