There seems to be a bug in the ISAPI-Module which prevents the server from sending any data back to the browser as soon as session_start() is called? 

My test data: 
<pre> 
<?php 
session_register("count"); 
$count++; 
?> 
Hello visitor, you have seen this page <? echo $count; ?> times.<p> 
</pre> 
stored as session_test.php and session_test.php4, where .php is executed by the ISAPI-Module and .php4 by the executeable php.exe. 
the .php-script returns "document contains no data", the .php4 works as expected.