Ext.grid.CheckboxSelectionModel Displaying two check boxes in single column in a grid

Hi All,

I am having a issue with Ext.grid.CheckboxSelectionModel which is showing two check boxes in a single column of a grid as addressed in attachment.My script is as shown below.I couldn't figure out the problem.And when i am selecting one check box second one getting deselect.This is the problem with ExtJS 3.4

Please help me out this.

Code:

new Ext.grid.CheckboxSelectionModel({
        checkOnly: 'true',
        header: 'Check',
        id : 'check',
        width: 76,
        mode: 'MULTI',
        listeners:{
            rowselect : function( selectionModel, rowIndex, record){
                    addNew(selectionModel, rowIndex, record);
            },
            rowdeselect : function( selectionModel, rowIndex, record){
               removeExisting(selectionModel, rowIndex, record);
          }
        }
       });

CheckBoxModel Problem.png



Ext.grid.CheckboxSelectionModel Displaying two check boxes in single column in a grid