I am using GarageBand '11, MacBook Pro 13", OS X Version 10.8.2. I just recieved this laptop today.
Whenever I try to use any loop or instrument that doesn't inititally come with GarageBand, I get the following message:
"The Software Instrument or Apple Loop Selected is not currently installed on your computer. Would you like to install the complete set of GarageBand instruments and loops?"
And from there I have two options. "Download Now" will open the App Store to Software Update, check for updates, and then tell me that there are no updates available.
The second option, "Download Later" is supposed to put the update into Software Update, for me to choose to download at a later time. Of course, this never shows up.
From this point, when you try again, GarageBand will give you a second message that says:
"The Software Instrument or Apple Loop selected is currently being installed. You have already initiated the installation of additional content for GarageBand via Software Update. For additional information please open the 'Software Update' application."
Of course, this is not true.
PLEASE NOTE that I have searched the Apple Support Communities already, and found multple people with success in deleting all GarageBand files, and then re-installing GarageBand. Virtually everyone has seen thier problem solved with this solution, and my problem still remained. Here is what I did:
I deleted the following folders / files:
Library/Audio/Apple Loops Index
As well as any GarageBand project files in my Music folder.
Please also note that the "Apple Loops" and "Apple Loops Index" folders were empty / or contained empty folders.
I then proceeded to re-install GarageBand from my "Purchased" section on my App Store. This, while successful on many other's MacBooks from the Apple Discussions, failed to fix the problem on my MacBook Pro.
I would LOVE if someone could direct me to a solution to this problem, or find a flaw in my process that I could fix. This is very important to me considering GarageBand was an important part of my decision in purchasing a MacBook Pro.