[ZPT] Formulator Problem

[beno]

Hi;
I have the following code in a ZPT page:

<table tal:define="form here/email_us_formulator" align=center>
   <tr tal:define="yourname request/YourName|nothing">
    <th align="left">
     <font tal:attributes="size python:here.sizeCalc2(5,here.size())"><font 
face="verdana"><b>
      Your Name:
     </b></font></font>
    </th>
    <td><input type="text" name="YourName"
               tal:replace="structure python:form.YourName.render(yourname)">
    </td>
  </tr>
...etc.

This renders like this:

<table align="center">
   <tr>
    <th align="left">
     <font size="4"><font face="verdana"><b>
      Your Name:
     </b></font></font>
    </th>
    <td><input size="20" value="" type="text" name="field_YourName"  />
    </td>
  </tr>
...etc.

When the form is submitted, it goes to a page with the following code:

Thank you, <p tal:replace="structure 
python:here.email_us_formulator.YourName">YourName</p>!

and renders like this:

Thank you, <StringField instance at 8f2dec8>!

What have I done wrong?
Furthermore, Formulator no longer validates at all for some reason. Why?
TIA,
beno