Missing Aif Files?, "what is it?" Options

[Tillonius]

hey everyone, I'm new to recording with logic express (and on macs).

Right now I'm just using it to record vocals. I import the audio file of the beat. Then I record all of the vocals in the other audio channels. everything is fine when I'm done, oh yeah, I'm saving the songs to an external harddrive. When I go to open Logic back up, and open the previously worked song it gives me the message: "'name of beat.aif' - what kind of file is this". Then when the song opens up the imported audio file (of the beat) is grey and does not play. When I try to re-import the beat ( the same way I did originally, the way that worked the 1st time) it gives me the same message.

Whats going on? can anyone help me out? I don't know if I'm saving the songs in the wrong manner or something. Thanks to anyone that can help me out.