If both your CNAME for WWW and @ A were updated simultaneously it is possible that the A record received an update faster than the CNAME record.
LINUX / MAC Command line
$ dig ns www.yourdomain.com <-- this gets your Name Server
$ dig @{NAME SERVER} www.yourdomain.com <-- this gets the information published by your Name Server(s).
If the above looks correct, then the registrar settings are correct and the site will become available once DNS TTLs expire (differs from person to person).
If the settings are not updated to the appropriate CNAME then please contact your registrar for support with respect to updating CNAME records.
The other possible reason you are arriving here is if the WWW or * record is currently configured incorrectly and pointing as an A record and not as a CNAME record. If this is the case, contact your account manager to find out what the CNAME should be.