After a lot of frustration and many waiting hours, I decited to backup all my data, perform a disk erase and a clean 10.8.4 installation (via the recovery process).
Then, first off all other software I installed the MainStage3, the basic installation as well as the additional download process worked perfectly and MainStage3 now rocks. The percentage of the download progress shown up immediately after a few seconds and the whole process took about 3 hours.
I assume that the conflict was caused by some other software installed on my macbook.
There is no problem with the programm installer itself, neither with the additional content download process.
It is maybe an extreme solution, but now MainStage works.
Hola, tuve el mismo problema, y lo pude solucionar!!!
Con estas 2 cosas:
1- Primero fui a: Apple, Preferencias del sistema, Seguridad y privacidad, General, Candado, puse clave, y luego: Cualquier sitio, y Permitir!
2- Al momento de instalar Mainstage 3, cuando aparece la primer ventana con el icono de Mainstage3 y el de Aplicaciones, arrastre el icono de Mainstage y lo solte dentro del icono de aplicaciones. Ahí se copio, y luego de eso no tuve más problemas...
Espero que a alguno le sirva mi solución, ya que estuve toda una noche sin dormir!!!!
I went though this until I deleted the app and re download it from App Store.
The biggest problem here is that progress bar. It honestly tells you nearly NOTHING.
Even IF your samples are downloading, you may not know it because the progress bar WILL HANG while it is actually working.
You need to give it an hour before you know it has failed, and that is on a 3Gb Internet connection.
When the samples have downloaded, the progress bar will go to about 75% and appear to hang again. This is the point at which the big bundle of files has been completely downloaded. Now your computer, Air in this case, has to decompress them all and move them where they need to go. THIS CAN TAKE ANOTHER 20 MINUTES (depending on what else your Mac is doing and the state of your storage--EVEN ON SSD), and you need to watch for when it starts, because you have to authenticate yourself as an administrator for the OS to write to the /Library folder where much of what you downloaded is going. If you fail to give an administrator password, eventually the installer will tell you it failed, when you could have stopped the failure by authenticating.
Thank GOD this only has to be done once. If you are a logic user, or Garage Band for that matter, you can also use those programs to download the critical content and then MainStage will start normally.