Hello,
I've just started using Kdenlive. I have 2 source clips, each 480p24 H264. I'll call them Clip A and Clip B. Here's what I have in my timeline.
Part of Clip A - Part of Clip B - Different Part of Clip A.
What happens when I render this section is that the last frame from the first Clip A ends up being rendered in front of the different clip A at the end, even though there's an unrelated clip between them. I've checked to be sure it isn't sloppy editing on my part by changing the last clip section in the timeline, and the effect remains. Does anyone know why this is happening, and what, if anything, I can do about it?

I was using the latest version as of the op. Trimming the clips doesn't fix the problem, it just changes which frame gets transposed. I'm thinking the cause is related to pulling the 1st clip from memory and then not properly seeking for the first frame. When I get home tonight, I'll try the latest version to see if it works any better.
Edit:
I've uploaded a sample video of the problem to youtube here: http://www.youtube.com/watch?v=VKe2gQmzaB8
At about the 38 second mark, the video transitions from the widescreen clip to the 4:3 clip, and the last frame from the previous 4:3 clip is rendered in front of the second clip. This frame is not supposed to be there, so moving the cut points doesn't change or fix the problem. I just upgraded to 0.8.0 release, and this problem still exists.