I have just tried connecting explicitly to 'http://www.server.com:8000' and then clicking on Site Wide Admin. What I get is a pop up window saying that I am about to enter a secure connection (to which I click yes) and then the browser's request line changes to 'http://www.server.com:8000/acs-admin' and the page doesn't load.
If I type 'https://www.server.com:8443/acs-admin', I get the admin pages without any problem.
Regards
Richard