Headers created with CGI-Session aren't included by IIS

[flowcontrol]

My code sets a cookie using CGI::Session. It works fine on my development server, but not on my client's server.

Both machines are running Windows 2003 Server, IIS 6, CGI-Session 3.95 and Perl 5.8.7.

On my server, the output is (literal line-end characters are shown for clarity):

HTTP/1.1 200 OK\r\n
Content-Type: text/html; charset=ISO-8859-1\r\n
Expires: Mon, 17 Apr 2006 23:04:20 GMT\r\n
Server: Microsoft-IIS/6.0\r\n
Set-Cookie: FLRCsurvey_email=; path=/; expires=Mon, 18-Apr-2005 23:04:20 GMT\r\n
Set-Cookie: FLRC_SID=dcedfa035893887cf0f7e9f6ac57765c; path=/base; expires=Wed, 23-Mar-2011 23:04:20 GMT\r\n
Date: Tue, 18 Apr 2006 23:04:20 GMT\r\n
\r\n

On the problem server, the output is:

HTTP/1.1 200 OK \r\n
Date: Tue, 18 Apr 2006 23:04:20 GMT\r\n
Server: Microsoft-IIS/6.0\r\n
\r\n
Set-Cookie: FLRCsurvey_email=; path=/; expires=Mon, 18-Apr-2005 23:04:20 GMT\r\n
Set-Cookie: FLRC_SID=dcedfa035893887cf0f7e9f6ac57765c; path=/base; expires=Wed, 23-Mar-2011 23:04:20 GMT\r\n
Expires: Mon, 17 Apr 2006 23:04:20 GMT\r\n
Date: Tue, 18 Apr 2006 23:04:20 GMT\r\n
Content-Type: text/html; charset=ISO-8859-1
\r\n

You can see that the Perl-generated headers are not being combined with the IIS-generated headers. The output in the browser, of course, is that the Perl-generated headers appear at the top of HTML page.

I've looked at the configuration of IIS, but can't find anything wrong. I can't reproduce the problem on the development server.

Although the problem (HTTP headers appearing in the browser) was observed using IE 6.0SP1, the output that I presented above was obtained using telnet. I just opened a connection to port 80 and sent:

GET /flrc/index.pl HTTP/1.1
Host: flrc-dev.host.domain
Accept: */*

There are no firewalls between the client and server machines at either of the respective sites.

So, does anyone have ANY idea where to look or what is causing this behavior?

Thanks!