The exact same thing is happening to me. We need to download 6.0.1 version because it's the latest that can run on Snow Leopard. Everything was perfect til today.
I also tried to recover the app from a backup (Carbon copy cloner) but it's not working.
I don't wanna upgrade to any other OS, and I don't need the fixes of version 6.3. We need 6.0.1 as it was working til today.

Quote Originally Posted by jazzhound View Post
The question still stands …
sounds like both of us can only upgrade to Snow Leopard, meaning the highest version of iReal Pro we can install is 6.0.1, so where can we find it to download?
In my case I have been using it without problem until now, yet my earliest available Time Machine backup from January of this year still says "iReal b is damaged and can't be opened. Delete 'iReal b' and download it again from the App Store."
The App Store only has the latest version, which won't run on Snow Leopard …