@GunnerP - the plugin cannot utilise any cookies from your browser or authenticating sessions. The way around this is to just save the html page to disk from your authenticated browser, and then drag/drop the html file into the url field.
It is a hidden feature that I had to incorporate for testing (the proxies at my work prevent calibre from accessing the internet directly) but as it turns out it should help solve such a problem. You don't need to save the whole web page content of course, just the html file itself. My plugin looks at the URL field, and if the url starts with file:// (which it will after a drag/drop) then it loads that html file locally rather than loading via a web browser...
Last edited by kiwidude; 08-17-2012 at 06:39 AM.