To start, I'm using Ubuntu Lucid Lynx. I'm running it on an Intel Mac (early 2010 I guess counts as a late 2009 model) and like most Linux Mac users want to be able to click and drag (my bug report is not about this though). I have been experimenting with trying to get numerous multitouch touchpad drivers working. I've downloaded all sorts of weird xorg drivers and dependencies and think that it may be the reason for this bug.
I've been using kdenlive for about 4 weeks without having any troubles. Recently my project/clip viewer did not display the visuals for my working project and for clips (the audio would still play just fine). I went under the Settings menu and changed my visual playback to be X11. I was had minor success in that. Now when I go to play the clips and the project the visuals display but its now transparent where if I have windows underneath the window (splash screen?) I see it in my display. If I have all windows but kdenlive minimized the display screen is still transparent and I can see my background in the image. This isn't something urgent but its just annoying and was curious if anyone had an starting recommendations of things or commands to use in the terminal so that I can help you better help me.

Oh and here are some images of the problem to better understand it.
In the project viewer you will notice these two petals of a flower that stand out on the viewer. That is part of my background. In the second screenshot it shows program windows that are underneath the kdenlive window. It doesn't even look like the project is playing but the audio works but the window below it obstructs the visuals in the viewer.

Maybe this helps:
http://kdenlive.org/user-manual/troubleshooting-and-common-problems/why-monitor-transparent-during-playback-works-when-d