Autocomplete problem using form.submit()

I'm having a problem with autocomplete when I try to use the form.submit() method in an onsubmit event handler. The following javascript code, which we use for disabling form double-clicks, also disables the autocomplete functionality of IE for some reason:

<script type="text/javascript">

var clicked = false;

function placeOrder() {
if (!clicked) {
document.forms[0].submit();
clicked = true;
}
}
</script>

If the forms.submit() call of placeOrder is removed, autocomplete works fine for the form. Any ideas on why this is occuring would be greatly appreciated.