Currently Being ModeratedNov 7, 2013 7:31 AM (in response to Arnoud NL)
I was able to solve this issue with help of the Appl tech guys. Because of the Mavericks update I needed to re-include my CVC code in the payment info of my account. In stead of telling me that during the purchase it just stalled.
I simplu went into my account / payment info and completed the info. After that, the in-app purchase of the additional loops worked again!
Success to others with the same issue.
Currently Being ModeratedDec 28, 2013 4:48 AM (in response to Arnoud NL)
I had the same problem.
Found out this happens when buying the extra content is the first purchase you do after installing Mavericks.
When you go to the app store, buy any app, and then go back to garagband and try again, it will work.
It did for me.
(bought an app I wanted anyway)
In my search for a solution I found another post that said it also works when you buy a song in iTunes, but I'm not sure about that.