Why don't you just set the focus on a link to the index page in HTML?
<a id="thelink" href="index.php">Click here or press enter to continue</a>
<script type="text/javascript">
<--
document.getElementById('thelink').focus();
//-->
</script>

IE7 requires a click to accept keyboard input to a flash object, anyway, so just doing it with JS and HTML is a better solution.