ILI9327 - working, but...

Hi

I have ILI9327 UTFT display - shield for arduino uno

and I have connected this to arduino mega. I think all is ok, but…

when I add this code on start

myGLCD.drawLine(0, 40, 390, 40);

it’s working fine,
but when I put this code:

  TSPoint p = ts.getPoint();

  if (p.z > MINPRESSURE && p.z < MAXPRESSURE) {
    myGLCD.drawLine(0, 40, 390, 40);
    Serial.println("XD");
  }

and touch the screen, serial monitor show “XD”, but screen gets white and it’s not draw the line

Please help