Petit probleme javascript :-)

<head>
<script type="text/javascript">

Image1 = new Image(88,244)
Image1.src = "http://www.lou-castelet.fr/project/pic/langbar.png"

Image2 = new Image(88,244)
Image2.src = "http://www.lou-castelet.fr/project/pic/ukover.png"

Image3 = new Image(88,244)
Image3.src = "http://www.lou-castelet.fr/project/pic/frover.png"

Image4 = new Image(88,244)
Image4.src = "http://www.lou-castelet.fr/project/pic/nlover.png"

function fr() { 
  var Obj = document.getElementById('switchlang');
  Obj.src = Image3.src;                            
  return true; 
}
function uk() { 
  var Obj = document.getElementById('switchlang');
  Obj.src = Image2.src;                            
  return true; 
}
function nl() { 
  var Obj = document.getElementById('switchlang');
  Obj.src = Image4.src;                            
  return true; 

}
function original() { 
  var Obj = document.getElementById('switchlang');
  Obj.src = Image1.src;                            
  return true; 
  }
</script>
</head>

<body>
<div class="center">
			<img alt="langbar" class="languagebar" id="switchlang" src="http://www.lou-castelet.fr/project/pic/langbar.png" usemap="lang" />
			<map id="lang">
			<area alt="francais" coords="122,43,25" href="http://www.lou-castelet.fr/project/" onmouseout="original()" onmouseover="fr()" shape="circle" />
			<area alt="nederlands" coords="189,43,25" href="http://www.lou-castelet.fr/home_nl.html" onmouseout="original()" onmouseover="nl()" shape="circle" />
			<area alt="English" coords="54,43,25" href="http://www.lou-castelet.fr/home_uk" onmouseout="original()" onmouseover="uk()" shape="circle" />
			<area nohref="nohref" shape="default" alt="noselect" />
			</map></div>
</body>

Configuration: Windows XP
Internet Explorer 7.0