Re: Accessing media redirects to 404 error
Just wanted to note that you don’t need to put the /wp-content/blog.dir/1/files/ line in your group documents URL
You should be able to put /files/ and it should still work.
This doesn’t solve your issue though.
You’re right about this line:
RewriteRule ^(.*/)?files/(.*) wp-content/blogs.php?file=$2 [L]
Your BP group documents are not being directed to blogs.php.
Did you check to see if any other files outside BP Group Documents work?
Try uploading something to the WP Media Library and see what happens.