One of the challenges in web design and web forums in particular, is how to handle the requirement to log in for more functional access.
Whenever a login prompt pops up, folks will often simply leave, rather than log in, even if they are already registered at the site. So immediate login isn't usually what you want to do with web forums; for one thing, you will lose folks who find your forums via search results that jump into forum content.
So web forums generally let you browse around until you want to do something that requires you to login, such as start new threads, reply to posts, etc.
Even at this point, I'm still inclined to give up rather than continue, when I see a login prompt. Why? Because I anticipate a hassle of not only login in, which I can handle, but having to re-navigate my way back to what I was doing - i.e. which forum, which thread, which one of 27 pages of posts (sometimes requiring 22 "next" because there's no "go to end" where the most recent stuff is found) and which post on that page, then the edit box I may have already started.
Microsoft's web reader for their newsgroups gets it wrong, at least in the context of linking to their forums via other Microsoft sites. Here's the repro; start here...
...and then at the bottom right of the page, right-click, Open In New Tab (the method I used, a straight click will likely do the same) on "Community Forums", taking you here:
So far, so good; we're in blah.blah.blah.ie8.blah which is where we want to be, and we start reading, then decide we want to post a new thread. Oops, now we want to login, so we do, and when we get back, we are no longer in the context of the newsgroup we wanted to visit. We didn't note the name of that newsgroup because we thought we'd always be able to link into it directly from the IE8 beta page.
Now I know Microsoft are battling to win over many of us usenet die-hards to embrace the web UI to their newsgroups. This is IMO a serious stumbling block, not only for us, but also for folks discovering newsgroups for the first time, without usenet preconceptions and expectations.
The above is as tested on XP SP2 with IE8 beta 1 installed over IE7, IE8 Standards Mode, set to prompt on active content, all such prompts OK''d.
Workaround 1: Remember what the newsgroup is called, duh! Not so easy in that it's not content that can be cut and pasted, in terms of the UI, and the nature of the data is a pain to remember. Breaks the concept of "let the PC do it", too, plus that only gets you back as far as the start of the newsgroup, before you navigated within it.
Workaround 2: Log in, then go back to the IE8 page and repeat the link to the forums (which Microsoft may also refer to as "communities"). This time you will navigate into a logged-in state, and all will be well, though any navigation you did within the forum would have to be re-done. For best practice (i.e. shouldn't be required, but...) remember to log out of both forum tabs when done.