I used an older version of the free player for years without difficulty. I purchased the licensed player yesterday and haven't been able to get even a simple setup to work. I've tried using the setup wizard and code samples from various parts of this site. So far no luck.
I suspect that I'm missing something simple, so I've included a bare bones page with the code in place. The "player-licensed.swf", "swfobject.js". and "video.flv" are all in the same directory as the html doc.
If anyone could point out the error of my ways it would be much appreciated!
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Test</title>
<script type="text/javascript" src="swfobject.js"></script>
</head>
<body>
<p id='preview'>The player will show in this paragraph</p>
<script type='text/javascript'>
var s1 = new SWFObject('player-licensed.swf','player','400','300','9');
s1.addParam('allowfullscreen','true');
s1.addParam('allowscriptaccess','always');
s1.addParam('flashvars','file=video.flv');
s1.write('preview');
</script>
</body>
</html>

You probably have the wrong version of swfobject.
See http://www.longtailvideo.com/support/forum/Bug-Reports/20102/Problem-with-JW-Flash-Player-4-6#msg134...