[Michael Stein]

This works for me, althouh it took me a bit before I realized BP_ROOT_BLOG was not defined.
In my case, when I checked, it was ID 1, so I defined it accordingly.

?>
<?php
//echo get_current_blog_id();

//echo ABSPATH . “<BR>”;
//echo get_site_url() . “<BR>”;
if ( !defined( ‘BP_ROOT_BLOG’ ))
define( ‘BP_ROOT_BLOG’, 1);

// echo “There is no root blog defined “;
// echo get_blog_option( 3, ‘siteurl’ ) . “wtf”;
/* This fixes the Multisite avatar problem */
function nfm_bp_avtar_upload_path_correct($path){
if ( bp_core_is_multisite() ){
$path = ABSPATH . get_blog_option( BP_ROOT_BLOG, ‘upload_path’ );
}
return $path;
}
add_filter(‘bp_core_avatar_upload_path’, ‘nfm_bp_avtar_upload_path_correct’, 1);
function nfm_bp_avatar_upload_url_correct($url){
if ( bp_core_is_multisite() ){
$url = get_blog_option( BP_ROOT_BLOG, ‘siteurl’ ) . “/wp-content/uploads”;

}

return $url;
}
add_filter(‘bp_core_avatar_url’, ‘nfm_bp_avatar_upload_url_correct’, 1);
?>