Typing ipconfig/dnsflush won't fix your problem, thats flushing the DNS cache, your problem is that your SWF file is being cached by the browser. There are a few ways to stop this. The easiest is probably by adding a random query-string onto the URL of the SWF file in the EMBED/OBJECT tag:
<script type="text/javascript">
<!--
document.write('<object etc ... ');
document.write('<param name="movie" value="filename.swf?r=' + Math.round(Math.random() * 99999) + '">');
document.write(' the other param tags here );
document.write('<embed src="filename.swf?r=' + Math.round(Math.random() * 99999) + '" etc .... </embed>');
document.write('</object>');
//-->
</script>
But be aware that this means your SWF will be downloaded afresh every time, and never from the browser cache. If you don't want this, consider adding a version number in the querystring rather than a random number, and increment this when you want clients to download a new SWF file.