Generating ArgumentError: Error #2008 parameter validity

Seems like this isn't the problem.  mx:Text is a halo component and uses TextField.  Something else going on?

Here's my fully filled out mxml file including your code.

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
               xmlns:s="library://ns.adobe.com/flex/spark"
               xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="955" minHeight="400">
    <fx:Declarations>
        <!-- Place non-visual elements (e.g., services, value objects) here -->
    </fx:Declarations>
   
    <mx:Text id="signUpBottomText"
             bottom="0" left="300"
             htmlText="{loginFooter}" selectable="true"
             styleName="ScreenBottomHeader">
    </mx:Text>

    <fx:Script>
        <![CDATA[
            [Bindable]
            private var loginFooter:String = 'Questions about domain or signing up? <font color="#29abe2"><a href="mailto:mailto:feedback@domain.com">Send us an email</a></font> and well get back to you the same day.';
        ]]>
    </fx:Script>
</s:Application>

Richard