I made the changes shown below...

void QwtPlot::setPlotLayout( QwtPlotLayout *layout )
{
if ( layout != d_data->layout )
{
delete d_data->layout;
//layout = d_data->layout; //Removed
d_data->layout = layout; //Added

updateLayout();
}
}
Is it my source only... It may very well be.
I just want to be sure..

Thanks