javascript error is null or not an object

Question

I am trying to open a window from a php script. But when I click I get this error

Line: 389 Error: 'surgExpressBuildDefaultButton' is null or not an object

Line 389 code is as follow

function setupLayout(i)
{
 document.body.onselectstart = function()
 {
  if (event.srcElement.tagName.search(/input|textarea/i)) return false;
 }

 setupButtons();
 if(window.parent.opener.parent.frames[0].surgExpressBuildDefaultButton)
 {
  buttonClick(window.parent.opener.parent.frames[0].surgExpressBuildDefaultButton);
 }
 else
 {
  layout.buttons.commonButton.fixSelected();
 }

 for(i = 0; i < da.imgPlus.length; i++)
 {
  da.imgPlus[i].onclick = clickPlus;
  da.imgMinus[i].onclick = clickMinus;
 }

 for(i = 0; i < da.spnName.length; i++)
 {
  da.spnName[i].selected = 0;
  da.spnName[i].title = da.spnName[i].innerText;

  da.spnName[i].onclick = function(){selectCommonProcedure(this);}
  da.spnName[i].ondblclick = function(){addCommonProcedure(this);}

  da.spnName[i].onmouseout = function(){this.className = (this.selected ? "nSelected" : "nOut");}
  da.spnName[i].onmousedown = function(){this.className = "nDown";}
  da.spnName[i].onmouseover = da.spnName[i].onmouseup = function(){this.className = "nOver";}
 }

 da.inpSearch.onkeydown = function(){if(event.keyCode == 13) updateProcedureList();}

 da.btnSearch.onclick = da.selSpecialty.onchange = updateProcedureList;

 da.btnClose.onclick = function(){window.close();}

 da.btnAdd.disable = da.btnSave.disable = CC.Disable;
 da.btnAdd.disable(1);
 da.btnAdd.onclick = addCommonProcedure;
 da.btnSave.disable(1);
 da.btnSave.onclick = saveExpress;
}

what could be the problem. Any idea?