Whenever I have this problem I can use the middle mouse button on the forum, which for google chrome opens up the page in a new tab, you could also right click and select open a new tab.
Also, you don't have to type out the whole thing, "nwnravenloft.com/forum" should work fine.
Edit: I also just tested opening this up in IE, which is the only versus of internet my work computers have which is the only place I've had this problem, and it gives this error message
This content cannot be displayed in a frame
