Arm7-based embedded doesn't refresh 7" touchscreen

I still have the same video refresh problem.
I developped an application on my desktop Linux-PC. When we tested the application on the OMAP3 3530 board (ARM7-based), touchscreen doesn't refresh correctly the same graphic behavior that I can see on my PC.
Example: if I use a push button to increase the value shown by an LCD, on my PC all is OK, but on the touchscreen I can see the updated value only if I colse the widget containg the LCD adn re-open it.
I tried update(), repaint(), qApp->processEvents(); but nothing to do!
Any suggestion?
Thanks
Paolo