Transitions and/or Effects do not apply to project


I have a problem with Video Effects and Transitions in several projects. I'm using Ubuntu 10.04 and Kdenlive 0.7.8 from the launchpad ppa.

I tried to make a Video with an Image Slideshow (for Youtube) with underlying music.

The Images shall be crossfaded and above this slideshow I wanted to lay an half-transparent SVG-Image as a logo that stays there all the time.

The audio is in Track 1, the logo in track 2 and the images for the slideshow in track 3.
Composite transition works well for the logo, but does not apply to the images. Sometimes (when i added a new image) it works for a short while, later then it doesn't.

I tried to use the "Fade to black" effect but I am experiencing the same odd things. Sometimes it works (I did manage to render the file correctly), but when I later open the same project without changing anything in between I have the same problem.

All I can say is, that it surely must be a problem in kdenlive, because live preview and redered files do not differ in any noticable way.