Qt Embedded messy code displayed on the screen

Hi,

I'm using Qt embedded 4.5.2 on an arm target board. There're some buttons and a 320x240 monochrome QVGA LCD on the board. The cross compiler is arm-linux.

My problem is: whenever a button is pressed, there will be some messy code displayed on the screen. Actually even when I run the application with -nokeyboard specified, this issue still occurs. It seems like the frame buffer is overlaped due to a button value is written to it. Then how to track this problem and fix it?

Any help is real appreciated.

Thanks，
Kevin