# change this in your template:
  <TMPL_RADIO PARAM="foo1" NAME="foo" VALUE="1">
  <TMPL_RADIO PARAM="foo2" NAME="foo" VALUE="2">

  # to this:
  <input type=radio name="foo" value="1" 
     <TMPL_IF NAME="foo1">checked</TMPL_IF>>
  <input type=radio name="foo" value="2" 
     <TMPL_IF NAME="foo2">checked</TMPL_IF>>