Lantiseptic Skin Protectant?
http://www.lantiseptic.com/product_skin_protectant.aspx
This is some heavy duty stuff. I've used it on double centuries and during long rides in the rain. It is a little difficult to get out of the chamois, but it certainly protects the skin. Good to use after you already have a rash from chaffing also.
Just make sure that you get the Skin Protectant as Lantiseptic makes a lot of other skin products which don't work for chaffing.
One other point: I was having chaffing problems after losing some weight. My daughter noted that my shorts were too baggy. She was right.