Current version of W3 Total Cache breaks the CDN functions (admin section) in a variety of way. For starters, often when I go to the CND details page after enabling on the General settings page, the CDN details page is blank.
When you can get things enabled and put in API key as well as a CNAME from the CDN provider (e.g., MaxCDN), I get a hostname error. This has been documented on several threads and is not unique to MaxCDN (Rackspace CDN and CloudFront as well).
So currently two issues:
1) Blank CDN details page
2) invalid "hostname" error
I tried rolling back from 0.9.3 to 0.9.2.11 but still had the same issues (probably because of settings stored from 0.9.3.