I agree it works in IE7. The q.cfc script is outputing JavaScript. In my case, it's outputing either the word "Available" or "Not Available".
I have modified a strip-down version of my code to work similarily as the one on co-opcookbook.com <script src="jquery-1.1.4.pack.js" type="text/javascript"></script> <script src="firebug/firebug.js" type="text/javascript"></script> <script type='text/javascript'> <!-- $(document).ready(function(){ // Execute the checkUsername on onBlur event $("#txtUserName").blur( function() { checkUsername(); }); }); // This will check if the username is already used by another user. function checkUsername() { var username = ""; // Removed Ajax result $("#username_status").html(""); username = $("#txtUserName").val(); $.get("http://server/AJAXCheckUsername.jsp?txtUserName=" + username, function(result){ alert(result); eval( 'var ' + result ); alert(ajax_result); }); } //--> </script> After running it in FF or Safari, I get the following : alert(result) => ajax_result = ""; ajax_result = "Not Available" alert(ajax_result) => Not Available The exact same code in IE7 gives me the "System error: -1072896658.". The code resides on the same server as AJAXCheckUsername.jsp Thanks