Can't hear audio while editing titles

Hello, I recently download iMovie 11 (version 10.0.8) after using iMovie 09 for a long time.

I have this problem: when i try to add and then edit the length of a title in my project, I can't hear the audio of the video. This use to help me to put the title clip in the right place, now is extremely frustrating if I can't hear where I'm putting it. How can I solve this? Thanks.