I have Kdenlive Version 0.7.8 running on Ubuntu 11.04 - the Natty Narwhal, when i load a video "AVI" and play the video the speed of the video go too fast, i now is only with "avi" i try with other video and works perfect, how i can i fix this problem with "avi" videos ?

Have a look here:
http://www.kdenlive.org/forum/solved-whats-wrong-audio-avi-file-help

This might be a sollution for you:
You should also try to simply remux to mkv or mov (mp4 is not really appropriate for mjpeg even it it works) without encoding the audio:
ffmpeg -i some.avi -vcodec copy -acodec copy -sn out.mkv

I had similar problem with .avi and those above solved my problem