LCD Problem

Hi all.
I am using qt embedded on my SEED-dec137 board.
Well, I have this problem, i can't figure out..
When i run qt applications, I have a lot of mess on the LCD, I can see that the application is jittering all around the screen. For example, When i run the framebuffer application i get these 3 rectangles jumping from point to point on the screen, really fast.
Despite of that, When I write these lines to the code:

Code:

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screenRect = new QRect(QApplication::desktop()->screenGeometry(QApplication::desktop()->primaryScreen()));
 QRect windowRect(0, 0, screenRect->width(), screenRect->height()); 
windowRect.moveCenter(screenRect->center()+QPoint(4,0)); 
setGeometry(windowRect);

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I get the application, set exactly on the LCD, with a little bit of shifting - the most left 4 pixels of each line appear in the right side of the Screen. Seems like these pixels overwrite the pixels that have been there.
so, whats the problem? whats wrong with the first (jittering), and with second (cyclic offset) ??