BuddyPress.org

You actually don’t want folder permissions as 777. On some hosts, 777 even cause an “Internal Server Error 500” error. It also means anyone and everyone can read/write/execute in that folder. At the most, you should have 755. Some hosts may differ on this, but in general, these rules follow. I don’t know that 755 will fix anything, but it may, so give it a try.

For the rest of the questions:

What kind of server are you hosted on?

What version of WP/WPMU are you using?

What version of BP are you using?