I am using PhpEd 6.0 build 6026 with the built-in server on Windows 7.  I find that when I try to upload a file using POST and multipart/form-data that the system freezes without ever reaching the target php page.  The same code works just fine on Windows 7 (64 bit) with IIS and PHP 5.2.12.
It's worth noting that the same code run on a 32-bit Windows XP machine with PhpEd 5.9 build 5933 works fine.  So it is possible that this is a 64-bit problem and it's possible that it's a 6.0 problem.  
Here are two sample files that demonstrate the failure:
File whbSend.php
 	
	
 
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
 
<html>
 
<head>
 
</head>
 
<body>
 
 <form enctype="multipart/form-data" action="whbReceive.php" method="POST">
 
    Send this file: <input name="userfile" type="file" />
 
    <input type="submit" value="Send File" />
 
</form>
 
</body>
 
</html>
 
 | 	
 
File whbReceive.php
 	
	
 
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
 
<html>
 
<head>
 
</head>
 
<body>
 
<?php
 
      echo($_FILES['userfile']['name']);
 
?>  
 
</body>
 
</html>
 
 | 	
 
When run under Windows/IIS, when you upload a file the WHBReceive file displays the file name.  When run under PHPEd, when you upload the same file the result is a blank page with no source.
PS:  This turned out to be a bug in the internal Web server SRV.  It was fixed in release 6030.