WordPress V 3.5.2 has broken my custom meta fields

Hello, I haven’t been able to figure it out yet but the method i’ve been using to save custom post meta data is no longer working. It’s been running fine for the past 2 – 3 years, and now suddenly today all of my sites that i’ve updated no longer save meta data. Does anyone have any information as to what’s happened or why?

I’ve been using the method outlined here: http://www.deluxeblogtips.com/2010/04/how-to-create-meta-box-wordpress-post.html

Any help would be greatly appreciated, i’m dieing here. over 40 websites i’ve built are no longer functional.