I know this topic was started 1 year ago but I thought I’d share my success story.
To start, I just want to note that I have the Permalink type set to Numeric.
First, in the Admin section, I went to Settings > General and changed the bbPress address (URL) from http://www.mysite.com/bbpress/ to http://www.mysite.com/forums/
Next, I renamed the directory /bbpress/ to /forums/ in my hosting account.
Finally, I opened up the .htaccess file in the root of bbPress and did a find a replace. I replaced “bbpress” with “forums” without the quotes. Saved it and reloaded the site.
Worked like a charm (for me)!