Help with cross-browser issue

Help with cross-browser issue

Let me start by saying this script works in Chrome, but not FF or IE. In FF/IE, the form will submit but the data will not post. 

Here's the javascript:

<script type="text/javascript">
$(document).ready(function(){
$("form#tweet_form").submit(function() {
var tweet = $('#tweet').attr('value');

$.ajax({
type: "POST",
url: "sidebar_right_tweet.php",
clearForm: true,
data: "tweet="+ tweet,
success: function(){
$(function(){
$('div.success').fadeIn();
$('div.success').delay(2000).fadeOut('slow');
});

}
});
return false;
});
});

</script>