When I try to update garageband (version 6.0.5) I get the message "You must have previously purchased the item being updated. Tap Buy to purchase it now.") The application came installed on my computer from new.
GarageBand (Mac) '11, Mac OS X (10.7.5)
That is because you cannot update an application that you did not already purchase from the App Store. Your version was originally installed from the iLife DVD.
If your system is from before July 20, 2011, then that would definitely explain some things.
I gather I have to purchase Garageband from the app store then? Is there no other way to update it?
No, Apple stopped updating the DVD-based versions in favor of the App Store. But then you never could update iLife without buying the new version, so nothing is really different.
When I try to update garageband (version 6.0.5) I get the message "You must have previously purchased the item being updated. Tap Buy to purchase it now.") The application came installed on my computer from new.
