I've been use kdenlive before a lot of times and i didn't had any problem before !
suddenly one day the monitors doesn't show the clip and show only the desktop ...
I tried to switch to x11 but its only half work !
http://img80.imageshack.us/img80/9046/127878842103.png
that picture is have x11 and using on ubuntu 10.04 .
the program doesn't do those problems on xterm mode and Guest mode !

Ty for helping !

I need real the help pleas ...
I want to get back to edit at kdenlive !
Atleast say me how to full reinstall of kdenlive that I will start from zero ...
Thank you for the helpers !

Did you update your system before you saw this problem the first time?
Is Compiz enabled?

Ummm at ubuntu 9.10 I didnt have that problem.
also after I've update to ubuntu 10.04 I didn't had this problem but one day it happend ...
So i try to fix it and I update my kdenlive to the lastest verision ...
And yet not working well ...
Also my compiz is On !

Please try to turn off Compiz then: http://kdenlive.org/forum/no-video-preview-window-ubuntu-lucid

Thank you for responding .
I've tried to set my visual effects to 'none' and switch it to x11 and its work fine !
but when i tried the visual effects on 'normal' its didn't work ... and it isn't comfort to me to use my linux without some effects.
so there is away to fix it without to close all the effects ?
If there isn't so it's ok I can stand it with out effects .
And thank you for helping me !

Unfortunately I have no idea what the exact reason is and how to fix it. Haven't been working on this parts of kdenlive. So I cannot give you a better solution, sorry.

But I've submitted a bug report. See here: http://www.kdenlive.org/mantis/view.php?id=1691

Simon

Ok I understand !
Thank you very much Simon !
Now I can back to edit at linux !
And again Thank You !

mvdstelt, do your jpegs have a width that is an odd instead of even number? Your problem is not related to compiz or playback driver/mode. Your problem is a bug in RGB to YCbCr (YUV) conversion. The reason you do not see it when paused is because Kdenlive uses RGB to display still frames; so no conversion takes place.