Comment 5 for bug 500059

Got it working. Don't know if it's a machine-specific fix or not, but here's what I did...

Go to Settings > Configure Kdenlive..., then select Playback on the left. Next to Audio driver:, select ALSA, and next to Audio device:, select whatever option you can (mine has ALC272 Analog, but I'm pretty sure that's specific to my netbook).

Restart Kdenlive, and you'll hopefully be on your way. I haven't had a problem since.

I read that alot of people were having problems using the PulseAudio drivers, which Kdenlive seems to want to use by default for whatever reason. Alot of people had to completely remove the PulseAudio packages from their computer, but I guess I lucked out.