BuddyPress.org

`
# BEGIN WordPress

RewriteEngine On
RewriteBase /
RewriteRule ^index.php$ – [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]

# END WordPress
`
works for me with permalinks set as Day and name
Try resaving your permalinks?