Re: forum does not work
I think there are probably a number of things that would cause that message but I doubt it’s permissions.
When you installed BuddyPress, did you get the forums working *before* any customizing (plugins/themes)? I’d recommend always doing this when installing or upgrading because it will help you to discover issues before you make customizations of your own.
I’m not sure what to advise, but you might try installing a completely vanilla (untouched) WordPress install in another subdirectory on your domain/server, and then install BuddyPress and and activate the forums on that test install.
If it works on the test install, something you customized along the way is causing the issue and you should begin removing/adding those customizations one by one to pinpoint the problem.