Combo box

Hi,

I am using flash cs 5.5. In my demo i crate a xml list .. it contain set of questions.I loaded all of them into combo box. When i finishe answer the question i want to remove the components for the gc. I am albe to remove the Combobox on normal state. But when there is the dropdown menu when i try to remove the component...the list remines there visible.I am not able to remove that.

code are:

//while(comboBox.numChildren>0)

     //comboBox.removeChildAt(0)      // no use

trace(comboBox,"----")      // output [object ComboBox]

comboBox.close();            // output error

trace(comboBox,"***")      // this line not at all printing.

comboBox.removeEventListener(MouseEvent.CLICK,restartTimer);

comboBox    = null;

Error msg:

TypeError: Error #1009: Cannot access a property or method of a null object reference.

    at fl.controls::ComboBox/close()

    at com.sample.elements.components::ComboBoxElement/dispose()

how to solve the issue?

Thanks,

Siva