For example,

<window mode="modal" onCancel="self.detach()" onOK="self.detach()" title="listbox" border="normal" width="400px">
The default selection is item1, but it shouldn't be selected at beginning.
<separator/>
<label value="listbox : "/>
<listbox mold="select">
<listitem label="item 1"/>
<listitem label="item 2"/>
</listbox>
</window>

If you remove the mode="modal", then it works well.