I request data of IAP items, which takes some seconds. When a user decides to go to another frame during this time, the app freezes. Happens always on iPod 3G with iOS 5.1.1, not all the time on iPad with iOS4.3

Can this be fixed? I don't want to force the user to wait by disabling the Quit Button until the requests are completed. Could also be critical when there's a connection problem, how do I know when to allow to leave the frame?