No sound in imported photobooth videos into imovie

Very frustrated, as I need to edit my photobooth videos in imovie. I can import them with no problems, but for some reason there is no sound in the videos when I import them into imovie - although there is sound when I use a diferent video converter and in garage band for example, but imovie seems not to recognise the audio in these videos.

Please help as I urgently need to edit these videos for a deadline and I can't do anything with them in imovie at the moment.

Advice greatfully recieved.

Many thanks