Funciona por lo menos para IE, en NS no lo probé..
Código:
<html>
<head>
<script language="JavaScript">
function cambiar(){
if (document.f1.hab[0].checked){
document.f1.habi.disabled = false;
document.f1.habi.focus();
}
else {
document.f1.habi.disabled = true;
}
}
</script>
</head>
<body>
<form name='f1'>
Habilitar <input type="radio" name="hab" onClick='cambiar();'><br>
Deshabilitar <input type="radio" name="hab" onClick='cambiar();'><br>
<input type="radio" name="habi" disabled ><br>
</form>
</body>
</html>
<hr noshade size=1><img src="http://www.gograph.com/Images-8712/ClipArt/cat03.gif" height="50" border=0 align="absmiddle"> <font size="2" face="verdana" color="#000000">
bet[/CODE]