The article is incorrect - the MAC ID is not the Media Access Key and is not the password. To get the Media Access Key, go to Messages & Settings, Account & System Information, Media Access Key. Use that as the password and you're in.
That's right, sorry. The similarity of the names confused me. The Media Access Key is what you use as the password, and is available on the screen described here.
Are you sure it's on your home network, e.g. is it getting programming information from your wireless network? Can you ping it from one of the machines on the network?
To get detailed help on certain problems, I found the TiVo Home Media Features & TiVoToGo forum at tivocommunity.com (
http://www.tivocommunity.com/tivo-vb/forumdisplay.php?f=35) to be a great resource. People there walked me through several problems I had as I tried various ideas in my research for the article.