I've been working on a project for a couple of weeks, and I finally got to the point of adding background music. The problem is that it doesn't work. The music only plays in parts of the project where there are no video, but only a title clip. As soon as it gets to the point where an actual video clip (with speech) starts, the music is muted. I want both audio tracks to be mixed together. How can I fix this? It has worked in my previous projects, and I even tried creating a new project with the same audio clip, and there mixing works just fine. I don't want to start from scratch with this project... I'm using Kdenlive 0.8.3 on Linux Mint 12.