From the article:
"With regard to encrypting data, you should keep in mind a recent case, United States v. Fricosu. Ramona Fricosu was accused of mortgage fraud. Asserting Fifth Amendment protections against self-incrimination, Fricosu refused to provide prosecutors with the password to her encrypted computer. A federal judge ordered her to provide the password or supply a decrypted hard drive to the police."

Can someone tell me why the Fifth Amendment didn't apply here?

Thanks for posting this article. Very useful info & links, some of which I may use in future for personal security reasons.