Error: 'getPositionEl().dom.parentNode' is null or not an object

Question

I had done functionality for pop up from tree panle in extjs...


problem is when i close the opened popup....and click on the other node ,the browser is the error...please verify the code and ammend some suggestions to make it out.....

var _fp = new Ext.FormPanel({
    //renderTo: Ext.getBody(),
    frame:true,
    //title : 'WorkFlow',
    method: 'POST',
    url: 'Default2.aspx', // dummy page, which spits back the variables passed through
    width: 500,
    autoHeight: true,
    //defaultType: 'textfield',
    monitorValid: true,
    bodyStyle : {
    padding: '10px'
    },
    /**
    After seeing the examples of this it's pretty easy, the one thing to rememember is if you don't want a random
    Colon (:) to appear in the top left when you enter no fieldLabel, use hideLabel, I think there's a bug for the Ext Boys.
     
    */
    items : [{
        fieldLabel: 'WorkFlowName',
        name: 'wfname',
        xtype:'textfield',
        allowBlank: false,
        blankText:'Enter WorkFlowname',
        msgTarget: 'side'
        , validationEvent: true


    },
     { fieldLabel: 'Description',
         name: 'desname',
         xtype: 'textfield',
        allowBlank: false,
        blankText: 'Enter Description',
        msgTarget: 'side'
    },
    {
        fieldLabel: 'Version',
        name: 'version',
        xtype: 'textfield',
        allowBlank: false,
        blankText: 'Enter Version',
        msgTarget: 'side'
    },
    {
        xtype: 'checkbox',
        fieldLabel: "Password Protected",
        boxLabel: 'A',
        inputValue: 'a'
   
       
    },
    {
        fieldLabel: 'Password',
        id: 'pwd',
        name: 'pwd',
    xtype: 'textfield',
    inputType: 'password',
    allowBlank: false,
    blankText: 'Enter Password',
    minLength: 6, maxLength: 32,
    minLengthText: 'Password must be at least 6 characters long.',
    msgTarget: 'side'
},
{
    fieldLabel: 'ConfirmPassword',
    name: 'CPassword',
    xtype: 'textfield',
    inputType: 'password',
    vtype: 'password',
    allowBlank: false,
    blankText: 'Enter ConfirmPassword',
    msgTarget: 'side',
    minLength: 6, maxLength: 32,
    minLengthText: 'Password must be at least 6 characters long.',
    initialPassField: 'pwd'
 
}
],
    // add some  buttons.
buttons : [
    '->',
    new Ext.Button({
    text : 'Finish',
    handler : function(){
    _fp.getForm().reset();
    },
    style : {
    display: 'inline',
    margin : '0px 5px'
    }
    })
    ]
    });

this is the formpanel am using...


and i wrote click handler for tree node like this..called the formpanel in windows



function() {
                var win = new Ext.Window({
                    renderTo: Ext.getBody(),
                    title: 'WorkFlow',
                    closable: true,
                    width: 500,
                    height: 500,
                    //border:false,
                    plain: true,
                    autoHeight: true,

                    items: [_fp]
                });

                win.show();
            }


first time its ok....after closing the window ,and  recliking the same node...i cant able to get pop up repeatedly.... and inj IE am getting this error....

Error: 'getPositionEl().dom.parentNode' is null or not an object..



help me out to make this successfulllll....


Thanks in Advance......