imovie 09 - where did all the audio go???

HELP!

I'm making a highlights DVD, and spent the last week going through 16hrs of video to pull out the best bits. I'm now about to start putting the bits together, but the audio has suddenly disappeared from the event! Does anyone know where it may have gone, or what I might have done please???


(it was working fine, and then I restored some rejected clips, and put them into another folder (where all the rest of the clips were stored on an external HDD) - I don't know if this means anything, but it was fine before I did this!)


What can I do? - I can't face starting from scratch!

I've been looking at it a bit more. In the event library, it plays video with no sound, but in the project library, it won't even play video. The only video it will play correctly is the section I exported to .m4v yesterday (a 1min clip)