If you have decided to update to iOS 5 -and therefore to iTunes 10.5 beta- and then you wanted to downgradeit is very likely that you have come across the iTunes error that does not allow you to load your iTunes library because it was created with a totally new version.

The solution is simple:

  1. Go to ~/Music/iTunes or wherever you have your iTunes library located.
  2. Rename the “iTunes Library.itl” file to “iTunes Library.itl.old”.
  3. Go to the “Previous iTunes Libraries” folder and grab the most recent file.
  4. Rename this file to “iTunes Library.itl” and put it in your iTunes folder
  5. Launch iTunes normally.

As you can see, the solution is not complicated at all, and in a minute it should be fixed without major problems.