Argg... maldito IE, no hay manera de que funcione
Os dejo todo el código, a ver si alguien ve algo mal...
Código HTML:
<label for="when1"><img name="A" id="A" src="yes.gif"></label>
<label for="when2"><img name="B" id="B" src="no.gif"></label>
<label for="when3"><img name="C" id="C" src="no.gif"></label>
<label for="when4"><img name="D" id="D" src="no.gif"></label>
<input CHECKED type="radio" style="visibility:hidden" name="when" id="when1" value="A" onClick="document.getElementById('A').src= 'yes.gif';
document.getElementById('B').src= 'no.gif';
document.getElementById('C').src= 'no.gif';
document.getElementById('D').src= 'no.gif'"/>
<input type="radio" name="when" id="when2" value="B" style="visibility:hidden" onClick="document.getElementById('A').src= 'no.gif';
document.getElementById('B').src= 'yes.gif';
document.getElementById('C').src= 'no.gif';
document.getElementById('D').src= 'no.gif'"/>
<input type="radio" name="when" style="visibility:hidden" id="when3" value="C" onClick="document.getElementById('A').src= 'no.gif';
document.getElementById('B').src= 'no.gif';
document.getElementById('C').src= 'yes.gif';
document.getElementById('D').src= 'no.gif'"/>
<input type="radio" name="when" style="visibility:hidden" id="when4" value="D" onClick="document.getElementById('A').src= 'no.gif';
document.getElementById('B').src= 'no.gif';
document.getElementById('C').src= 'no.gif';
document.getElementById('D').src= 'yes.gif'"/>