Ok, so I have a Macbook Air, iPad and iPhone. I normally use an external HD for my photo and music library due to lack of space on the Air. I signed up to iTunes Match, thinking that I would be able to listen to music without carrying my external HD with me every time as my music collection would be in the cloud. iTunes Match matched half the tracks and uploaded the rest. Now when I play them on the Air, half of the tracks play, while the others says 'File could not be located' which it normally says when my HD is not plugged in. What's going on? Isn't is supposed to play regardless or am I in the wrong? Any help?