Flickering screen and inactive rendering

i'm having some issues using kdenlive 7.5 when trying first to read AVI files in the project monitor window, and then for rendering a project.
The first problem is about the project monitor window which is always white when reading a video; I "work arounded" it by launching kdenlive with "env XLIB_SKIP_ARGB_VISUALS=1 kdenlive". But this is just a workaround, and any other solution is more than welcome!

The second issue i'm having is probably more critical: when trying to render a project, (even in AVI), after I launched the rendering, the render window is flickering, I have tons of sub-messages displayed on the screen, always the same repeating many times.
I deactivated compiz, and the rendering worked... but only once.

From what i read in other rendering topics, I'm suspecting bad MLT&ffmpeg or freir plugins versions (those ones were already installed before kdenlive 7.5), but I could not find what are exactly all the packages to remove and reinstall.

So i'm looking for those packages names to delete and reinstall....

I'm using Ubuntu 9.04 and I installed kdenlive 7.5 using the packages of this website.

Thx in advance for your help