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?