Because of the use case, I could do otherwise. Instead of actually disabling the buttons, I would simply not allow the submit action to work until the page is loaded. This does not require any changes to existing HTML to work, and your pages will not be useless when disabling JS:
<script>
$('input:submit').live('click', function () {
return false;
});
$(window).load(function(){
$('input:submit').die();
});
</script>
: , script jQuery <head>, , . (, ).