Show busy on panel with borderlayout is not working

<zk>
	<hbox>
		<button id="btn1" label="Show Busy" onClick='Clients.showBusy(panel, "Busy")'/>
	    <button id="btn2" label="Clear busy" onClick="Clients.clearBusy(panel)"/>
	</hbox> 
	<div id="div" height="75%" >
		<panel id="panel" height="100%" title="test">
			<panelchildren>
				<borderlayout>
					<center>
						<div id="divTwo">
							<grid id="grid" 
								fixedLayout="true" width="75%">
								<rows>
									<row>
										<textbox />
									</row>
								</rows>
							</grid>
						</div>
					</center>
				</borderlayout>
			</panelchildren>
		</panel>
	</div>
</zk>