Вроде должно работать
<head>
<script type="text/javascript" src="http://yandex.st/jquery/1.4.2/jquery.min.js"></script>
<script type="text/javascript">
$('input').live("keydown", function(e){
var e = e || event, k = e.which || e.button;
if(e.ctrlKey && k == 86) return false;
});
</script>
</head>
<body>
<input type="text" >
</body>