WCCP users should be redirected to the SSL Login page through the Smoothwall Filter WCCP transparent interface. When users use WCCP and have their Smoothwall Filter WCCP transparent interface set to redirect to the SSL Login page, the SSL Login page redirects using a redirect to the host name.
Any issues with this will be due to missing DNS entries for the host name. It is a WCCP requirement that the client machines be able to properly resolve the host name via DNS. Check your DNS entries are up to date.