I am assuming you are only having this issue in IE?

Try this:

1. Undo Autoheight in IFrame settings.
2. Add the following to "onclick" parameter "onload (Javascript)" field (under Other Options): resizeIFrame(this)

3. Add the following javascript to the Page Settings > Advanced Settings > Page Header Tag

<script type="text/javascript">

function resizeIFrame(ifr)
{
 if (!document.all)
    ifr.style.height = 1;

 var ifrSrc = ifr.contentWindow.document.body;

 var the_height = ifrSrc.scrollHeight;
 ifr.style.height = the_height;
}
</script>

See if this will do the trick.  And, PLEASE, let me know if it does (or doesn't, of course).

Under Edit IFrame Options > Other Options  there is a field called "onload (Javascript):" - put that value there, please.