switch_to_blog() not working

I am currently writing a plugin for Multisite, and in it, I need to switch to the blog that is using the plugin.

$blog_id    = $_POST['blog_id'];
switch_to_blog($blog_id);
//  PLUGIN DOES STUFF
restore_current_blog();

In the above code, I’ve verified that $blog_id is the id of the blog I need (in this case, it’s 37). The value returned from the switch_to_blog function is ALWAYS 1, and the plugin does stuff to blog id 1.

$wpdb->set_blog_id($blog_id);
//  PLUGIN DOES STUFF
restore_current_blog();

This code switches to the desired blog id.

http://pastebin.com/GDBdiqYU