Edit: After half day, my wife’s Mac started having the same problem. I have then applied the solution that I found in the Apple
Apple Seads iTunes 10.5 beta 9 to Developers –
Apple has today released the iTunes 10.5 beta 9 to developers.We have not had a iTunes beta released for three weeks. The release of beta 9 could can suggest we are going to see the official iTunes 10.5 launch at Apple’s Media event on October 4th.
MacRumors published a list of issues from the release:
– “Scan and match” feature is not yet complete. Some users’ tracks may not be recognized by iTunes Match even if the tracks are available in the iTunes Store, and those tracks will be uploaded to the users’ iCloud storage. Some tracks may also be mis-matched to a different version of the same song on the iTunes Store.
– Music can only be added to iCloud from one computer at a time.
– Updating an iOS device to iOS 5 beta 7 may result in music failing to play. Users should turn off iTunes Match in settings and then turn it back on to restore functionality.