I was having the same troubles as the original poster. WordPress 2.8 and BBPress 1.0 RC2, whenever I logged into BBP I couldn’t log into WP without logging out of BBP first. All the settings matched in both configs and adding in the suggested code (be it from the WP plugin which gave me a COOKIEHASH, a COOKIE_DOMAIN, a SITECOOKIEPATH, and a COOKIEPATH or from the BBP integration page which gave me just a COOKIE_DOMAIN and a COOKIEPATH) didn’t change anything. I tried junsuijin’s suggestions and now when I log into one it logs me out of the other. Anybody know how to get this running properly?