HTTP Error 401.2 - Windows 2003 X Squid

Pessoal,

Tenho um servidor SuSE SLES 9.0 com Squid Cache: Version 2.5.STABLE12. Usei a configuração : configure options: --enable-storeio --enable-snmp --enable-default-err-language=Portuguese --enable-basic-auth-helpers=NCSA --enable-ntlm-auth-helpers.
Está autenticando normalmente, mas quando tento acessar um servidor Windows 2003 que tem uma que solicita autenticação, acontece o seguinte erro:

You are not authorized to view this page
You do not have permission to view this directory or page using the credentials that you supplied because your Web browser is sending a WWW-Authenticate header field that the Web server is not configured to accept.
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Please try the following:

Contact the Web site administrator if you believe you should be able to view this directory or page.
Click the Refresh button to try again with different credentials.
HTTP Error 401.2 - Unauthorized: Access is denied due to server configuration.
Internet Information Services (IIS)

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Alguém sabe resolver isso ?