What google is doing is simply considering the site with and without the "www" as different websites. There is nothing wrong with this and should be considered this way because lots of people out there use various subdomains for different sites. It just so happens that with the www and without are pretty commonly the same site but this is not always the case.
For example:
http://adultplatinum.com/
http://www.adultplatinum.com/
Two completely different sites...
WG