Interestingly if I manually reregister the msls column in functions.php the column shows up again.
/* Fix admin column msls column conflict */
function add_msls_column( $columns ) {
$arr = array();
$blogs = MslsBlogCollection::instance()->get();
foreach ( $blogs as $blog ) {
$language = $blog->get_language();
$flag_url = MslsOptions::instance()->get_flag_url( $language );
$icon = new MslsAdminIcon( null );
$icon->set_language( $language )->set_src( $flag_url );
$arr[] = $icon->get_img();
}
$columns['mslscol'] = implode( '?', $arr );
return $columns;
}
add_filter( 'manage_posts_columns' , 'add_msls_column' );