Why doesn't OnSubmit validation work for text fields on my record edit page?

I'm been puzzling over this for a while. Why doesn't OnSubmit validation work for text fields on my record edit page? For example:

Email Address: <cfinput type="text" name="UserEmail" value="#form.UserEmail#" validate="email" required="Yes" validateAt="onSubmit,onServer" message="Please enter a valid email address." size="35" tabindex="8" />
       
If I enter no value in the text field, then I see the error message in OnServer validation, which is less friendly and more forbidding than the friendly pop-up alert window of onSubmit validation.

When I view the source of the edit page, I see the ColdFusion-built script that creates the onSubmit alert window:

<script type="text/javascript">/* <![CDATA[ */
	if (window.ColdFusion) ColdFusion.required['firstname']=true;
/* ]]> */</script>

<script type="text/javascript">/* <![CDATA[ */
	if (window.ColdFusion) ColdFusion.required['UserEmail']=true;
/* ]]> */</script>
<script type="text/javascript">
<!--
    _CF_checkCFForm_1 = function(_CF_this)
    {
        //reset on submit
        _CF_error_exists = false;
        _CF_error_messages = new Array();
        _CF_error_fields = new Object();
        _CF_FirstErrorField = null;

        //form element firstname required check
        if( !_CF_hasValue(_CF_this['firstname'], "TEXT", false ) )
        {
            _CF_onError(_CF_this, "firstname", _CF_this['firstname'].value, "Please enter your first name.");
            _CF_error_exists = true;
        }

        //form element UserEmail required check
        if( !_CF_hasValue(_CF_this['UserEmail'], "TEXT", false ) )
        {
            _CF_onError(_CF_this, "UserEmail", _CF_this['UserEmail'].value, "Please enter a valid email address.");
            _CF_error_exists = true;
        }


        //display error messages and return success
        if( _CF_error_exists )
        {
            if( _CF_error_messages.length > 0 )
            {
                // show alert() message
                _CF_onErrorAlert(_CF_error_messages);
                // set focus to first form error, if the field supports js focus().
                if( _CF_this[_CF_FirstErrorField].type == "text" )
                { _CF_this[_CF_FirstErrorField].focus(); }

            }
            return false;
        }else {
            return true;
        }
    }
//-->
</script>

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However, the onSubmit alert window does not appear. I've read the documentation and think I am doing things correctly:
http://help.adobe.com/en_US/ColdFusion/9.0/Developing/WSc3ff6d0ea77859461172e0811cbec0ffd8-7fea.html

What am I missing? Thank you as always.

Eric