The html.tlp.php has:

  <!DOCTYPE html>

With this, in IE, the CSS position: fixed; doesn't work.

Changing it to:

  <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

fixed it.

Glenn