Nextgen Gallery for wpmu 2.9+

To make Nextgen Gallery for for Wpmu do this,

Open
admin/install.php

Find this line (around line 135)
function ngg_default_options()

Change this
$ngg_options['gallerypath'] = 'wp-content/gallery/'; // set default path to the gallery

To
$ngg_options['gallerypath'] = “wp-content/blogs.dir/” . $blog_id . “/files/”; // set default path to the gallery

And everything should work!