Do you have 2 @ A records? There should be only be the one I listed. If you need my help, email the domain to the help desk if you do not want to post it here. I may need to take a look.
Oh, and just re reading this. The www record must point at domains.smugmug.com not your smugmug address. That is a key thing that needs to change that may help.
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Add that to your domain host DNS records and it should fix things up after a couple hours to refresh.
If you have trouble, let me know.
http://help.smugmug.com
My A (host) does "point" to 208.79.45.23 as it has since creating the account. Under Cnames I have www pointing to mydomain.smugmug.com. (Godaddy)
Oh, and just re reading this. The www record must point at domains.smugmug.com not your smugmug address. That is a key thing that needs to change that may help.
http://help.smugmug.com