[elemeno]

It sounded like that's a result of the upgrade on Android - presumably they've changed something recently about how they store the offline play lists.

[Shank]

Offline playlists are encrypted by Spotify. Presumably this change means that the encryption keys used by Spotify to store offline data were compromised.

[pionar]

Actually, it looks like the "upgrade" is actually a new app entirely, so it's probably just that since it's a new app, the offline data has to be regenerated.