http://english-grammar-mistakes.blog...vs-proven.html
Here's a good explanation. It mentions the obvious to English speakers
that the word proven must be used if it takes the role of an adjective.
As Rusty and I have written, as past participles proved and proven are often interchangable. The interesting point made is, according to the blog,
proved is the preferred past participle in British English while
proven is preferred in North America.