I'm copying an album of non-DRM songs from iTunes (where they all play just fine) to an iPad. Three of the songs on the album were downloaded through the Bandcamp purchase interface (let's call it method A), and they transfer fine, but the rest were downloaded directly as .mp3 files (method B), and do not transfer. Rather, they ostensibly do: the song appears in iTunes and in Music.app, but does not play in either and appears greyed out in iTunes with a grey sync icon next to it.
There are several other albums also gotten by method B, which all transfer completely fine. What in the world is going on, and how can I fix it?
I am running Mac OS 10.7.3, iOS 5.0.1, iTunes 10.5.3 (3), and am using an iPad "1". I've already tried deleting them from the iPad and re-copying, but it still only copies the three "A" songs.