<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.2.6/jquery.min.js"></script>

<script type="text/javascript" charset="utf-8">
$(document).ready(function(){
	$('.lala').click(function(){
		console.log($('#test_broken').attr('action'));
		$('#test_broken').attr('action', 'bar');
		console.log($('#test_broken').attr('action'));
		
		console.log($('#test_working').attr('action'));
		$('#test_working').attr('action', 'bar');
		console.log($('#test_working').attr('action'));
	});
})
</script>

<form action="foo" method="post" id="test_broken">
	<input id="action" type="hidden">
</form>

<form action="foo" method="post" id="test_working">
</form>

<input type="button" class="lala" value=" Test 1 ">