Here's some quick code that should add this behavior to all graphical radio buttons on the page:
<script>
$(document).ready(function(){
var resps = {};
$('input[type="radio"]').each(function(){
var name = $(this).attr('name');
if (!resps.hasOwnProperty(name)) {
resps[name] = SSI_GetValue(name);
}
});
SSI_CustomGraphicalRadiobox = function(graphical, input) {
var name = $(input).attr('name');
var resp = SSI_GetValue(name);
if (resp != 0 && resp == resps[name]) {
SSI_RadioReset(name);
resp = 0;
}
resps[name] = resp;
};
})
</script>