Hi April,
I have the same issue. I see it got fixed on your website, even though you got no answer here: how did you do it?
PS and yes, even with Premise switched off it gets you a 404 instead of asking you to login (which I guess it ought to)
Yup, I just switched over from SimplePress to BBPress and I have this issue.
I switched off all plugins except Premise – which I need to give my students entrance to the member site – and nothing gives. They still get the 404.