I know you said you have, but just to double check, have you gone into Privacy Controls (in NPF), Advanced, and added the website to the list, which you can then configure access to? Can you not access the site at all, or is it just the forum you can't post on? I can get into the site on NPF 2005, without altering any settings.
Other than that, do you have ad blocking enabled, or a high cookie setting? Can't think of anything else myself, but someone else might.