"Please make sure that on your account profile, the birth date is set correctly. When the birth date on the account profile is a minor, Privacy setting can only be set to Contacts only."

This restriction is meant to protect minors from predator and fraudulent phone calls.

Oops. It turned out that my friend had not wanted to reveal her true birthdate when setting up her Skype profile. So she made one up. Unfortunately, the date she entered made her a minor. So she went back and changed the birthdate in her Profile. She was now an adult. Next, when she tried again to change her Privacy settings, they survived a restart. Finally!

I remain perplexed as to why Skype keeps this Privacy settings restriction for minors such a secret. If it's designed to comfort parents, wouldn't you want them to know about it?