Show hide component using Ajax

I'm using ajax to show or hide text field which is used to search for a certain user(method invoked sets variable which determines whether text field should be rendered or not).In most cases it works(I click on link several times),but sometimes it won't rerender text field,then it works again.Can someone tell me why this happens.Thanks!!!
This is the page where I'm trying to do that:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
   "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<f:view xmlns="http://www.w3.org/1999/xhtml"
	xmlns:ui="http://java.sun.com/jsf/facelets"
	xmlns:f="http://java.sun.com/jsf/core"
	xmlns:h="http://java.sun.com/jsf/html"
	xmlns:a="https://ajax4jsf.dev.java.net/ajax"
	xmlns:s="http://jboss.com/products/seam/taglib" contentType="text/html">
	<html>
	<head>
	<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
	<title>Baza_znanja</title>

<a:loadStyle src="/stylesheet/main.css" />

</head>
	<body bgcolor="#0000CC">
	<div id="main_body">

<div id="site_logo"><img src="img/logo.png" /></div>
	<div id="links">
	<table align="center">
		<tr>
			<td>
			<div id="link_item"><h:outputLink value="conferences.seam">Konferencije</h:outputLink></div>
			</td>
			<td>
			<div id="link_item"><h:outputLink value="trainings.seam">Treninzi</h:outputLink></div>
			</td>

</tr>

</table>
	</div>
	
	<div id="welcome_panel">
	<table align="center">
		<tr>
			<td></td>
			<td align="center"><a:form>
				<h:commandLink value="Find user">
					<a:support immediate="true" reRender="searchUser" event="onclick"
						action="#{myBeanClass.SetSerchUserVisibility}" />
				</h:commandLink>
			</a:form></td>
		</tr>

</table>
	</div>