i-Movie '11 silence

Hello,

I've been using i-Movie for a few months yet to make very short video clips for work. I convert videos to DV before importing them into i-movie, and a make clips of less than a minute. This has been working fine, up until today. Each "new event" that I import plays fine, but has NO SOUND. The finalized projects all play sound, but there is no corresponding image. And the not finalized projects are not doing anything at all. This seems very mysterious to me. Any thoughts???

Much appreciated!