In PaniniSlide.cpp the following causes your flash:
Qt Code:
  1. // set checkbox text, hide it if none
  2. pcheckbox->setText( checkText );
  3. pcheckbox->setVisible( !checkText.isEmpty() );
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You have four controls that pass a non-empty QString.

To eliminate the flash, try giving pcheckbox a parent:
Qt Code:
  1. pcheckbox = new QCheckBox(this);
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