Problems with iMovie Exporting

I play World of Warcraft, and I use the in game recorder to record boss kills on my Mac. I then use that footage in iMovie to make movies on youtube.
I've been having problems lately however.
Whenever I export the movie to a file on my machine, the audio that I've put into it (and usually edited myself) doesn't export with it. There's no sound on the finished .mov file. Why is this? It's happened 3 times in a row. Is that a setting that I've accidentally unchecked or something? It never did this before. It always put the footage+audio into a single .mov file.