@Danwp23 Hello, I was having this same issue when I came upon your post. I had not tried changing the permalinks yet but did and had the same successful result as you (no 404). I changed the permalinks back to the post name structure then changed the theme package under the forum settings to Twenty Ten instead of bbPress Default. Refreshed the forum page and IT WORKED! The only conclusion I can make is there may be a issue with the bbPress Default theme package and some custom themes. Let me know if this works for you, hope so!