Update… I found this thread
Logout error when bbPress plugin is active
which suggested to comment out lines 938 and 939 of bbp-user-template.php.
Doing that makes the 404 go away. But now I’m being redirected to my S2member login welcome page… which I don’t want. I want forum users who log in to be re-directed to the last forum page they were on. Seems like that’s what bbpress is trying to do, it’s just adding an extra subdomain in the forum url.
Sorry for the bump. Just thought I would add that info in case it helps.
The patch mentioned above fixes my logout redirect problem, but the login still redirects to a 404 b/c it’s still adding the sub-directory name to the URL twice. Any advice very welcome!