Speed not working properly

"Speed" effect works well if I speed up or if I use Strobo, but the slow-mo doesn't work very well.

These are the problems I have:

- If the original clip is not a DV source, the effect returns a black screen
- "End" point doesn't work: if I set "Start" 50 and "End" 50, the clip starts at 50% but ends at 100%, as I didn't set the End point.

I'm on Kubuntu Feisty, using Kdenlive 0.4 from Ubuntu package files downloaded from the main site (with the two necessary libraries previously installed from the same downloaded package).

Have you noticed the same problem?