A quick super search for "Content-Type:" returned several results; 521635, specifically abcde's response, may contain what you're looking for.

update: The basic idea of the linked node is that the header may be already written by IIS causing your header to be a duplicate./update

You could test this using telnet to connect to your webserver to view the headers:

telnet localhost 80
GET /

[download]

In reply to Re: Activestate on IIS 5 by beachbum
in thread Activestate on IIS 5 by Anonymous Monk

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