Movabletype 3.16 login bug

I upgraded to Movabletype 3.16, and it has an annoying bug for users who have it installed in the root directory of a domain or subdomain, as I do: it refuses to stay signed in, kicking you back to the login form between every click and every action. The problem is a few lines in lib/MT/, but the fix suggested in the MT support forum is rather cryptic. Thankfully, has a mofidied ready to download.