jquery validate TypeError: c is undefined

jquery validate TypeError: c is undefined

Hi, I'm fairly new to using jquery and plugins.  I'm trying to use jquery validate and I get an error "TypeError: c is undefined" in the Browser Console using Firefox when the form event fires. 

Here is my test code:

<html>
<head>
<meta charset="utf-8">
<script src="js/jquery.validate.min.js" type="text/javascript"></script>
<script>
$().ready( function() {
$("#userName").validate();
});
</script>
</head>
<body>
<h2>jquery validate plugin testing</h2>
<form name="register">
<input type="text" name="userName" id="userName">
<input type="submit" value="Submit">
</form>
</body>
</html>

I appreciate any help if you understand this issue.  Thanks!