jquery execute $.post on second click in IE

[genia]

i got this simaple code:

$(document).ready(function(){
	$("#pac").click(function(){
	$("#pac").animate({marginTop: "17px", paddingBottom: "17px", borderBottom: "2px solid white"}, 2500 );
	$.post("rpc.php", {u:"genia"}, function(data){
		            if(data.length >0) {
           $("#pac_c").append(data);
           	            }else{
			$("#pac_c").css({overflow: "none", display: "none"});	
			}
		$("#pac_c").css({overflow: "auto", display: "block"});
			
        })});
	});

it works prefect in FF but in IE i need to click again for the script to do the $post.

any way to solve this?