prova così:
codice:
<script>
function enable(){
if(document.getElementById('radio1').disabled){
document.getElementById('radio1').disabled=false;
document.getElementById('radio2').disabled=false;
document.getElementById('radio3').disabled=false;
}else{
document.getElementById('radio1').disabled=true;
document.getElementById('radio2').disabled=true;
document.getElementById('radio3').disabled=true;
}
}
</script>
<form name="formus">
<input type="checkbox" name="abilita" value="abilita" onclick="enable()"/>
<input id="radio1" type="radio" name="radio1" value="1" disabled="true"/>
<input id="radio2" type="radio" name="radio2" value="2" disabled="true"/>
<input id="radio3" type="radio" name="radio3" value="3" disabled="true"/>
</form>