this is my checklist for you
1. make sure that your dyndns address is pointed at your server, or network as the case may be. In my case I use a little app on a windows machine in my network that keeps my external ip address current and my domains pointing to it. You can find this little deal somewhere on dyndns's site.
2. I believe it works best when your setting up a site to put in the hostname field the firstpart of your domain ie: eron Then where it asks you for your domain name put in hobby-site.com
This is what worked for me and its probably not a complete answer but I hope it helps.