JSF 1 gridpanel getter method doesn't get called on load second time

Question

Tomahawk library has been used in the legacy J2EE web application . The jsf page contain the below line ( gridpanel control) :

 <h:panelGrid binding="#{BasicUnavailability.gridPanel1}" id="gridPanel1" border="0" columns="8" width="100%"/>

There are comboboxes inside gridpanel which would be generated dynamically by the getter method which does processing and adds comboboxes to the gridpanel and return it :

 public HtmlPanelGrid getGridPanel1()
{
    //some processing 
    //add comboboxes to grid
   return gridpanel1;
}

And the setter :

public void setGridPanel1(HtmlPanelGrid gridPanel1) {
        this.gridPanel1 = gridPanel1;
    }

When this page loads for the very first time gridpanel1 getter method is called and filled with comboboxes. It uses some session scoped bean also for processing. When we navigate away from this page and come back to this page this getter method doesn't gets called and earlier populated gridpanel will be shown .

This problem seems to be related with this SO thread.But I am not able to figure out the problem with JSF1.0 . Please provide your valuable suggestion .