HTML source code is cut off in some cases with Windows 2003 SP 1, IIS, PHP 5.0.4, CGI/FastCGI

Hello I have a problem with Windows 2003 SP 1, IIS, PHP 5.0.4, CGI and FastCGI. In some cases the PHP generated HTML source code delivered to the client is cut off. Not the whole HTML source code ist deliverd. This occurs not regularly. Example: call page test.php -> the site is well displayed. Open a new browser window, call the same page -> the last part of the page will not be displayed. I can't figure out a rule. Sometimes it works sometimes it doesn't. I tested the problem with the following installations: Error occurs: - PHP 5.0.4 CGI - PHP 5.0.4 CGI with Zend Optimizer - PHP 5.0.4 FastCGI with Zend WinEnabler 1.2 No Error: - Static HTML file - PHP 4.3.7 CGI - PHP 4.3.9 FastCGI mit Zend WinEnabler 1.2 - PHP 5.0.4 ISAPI This error occurs only after updating our test server to SP1. Thanks, Marco Abächerli