If I remember correctly, the DRM-encryption for Zune Pass content always used a really low-level system, with bits going all the way down to the kernel. With WP8 and Windows 8 both running new kernels, and new encryption schemes for Xbox Music, it makes sense that Zune pass content wouldn't switch over nicely. Doesn't ease the sting for those with large collections, I know, but I've always found it at least makes it better knowing there was a rationale and context behind something like this and not it just being an arbitrary frustration.