Transitions don't work on png images with transparency

Hello! I want to make a video with several png images with several tracks video. But if the png image has the transparency effect, it doesn't allow to add a transition. Also if I put another image in the second track the transparency effect doesn't work, because I want to see both images. I have worked with Cinelerra, but in this time I would like to make a new video with Kdenlive. Please tell what I can do, or simple Kdenlive doesn't have that option.

Here you can look the video I made with Cinelerra http://youtu.be/UgAkQwYmkMg and I would like to make a similar video but with Kdenlive.

Thanks