My personal experience has been that using a dyndns address when on the same local network as the server is iffy at best. The dyndns address should work if you take the device to another network, but unless you make some configuration changes, the server may not recognize its own address. I'm not really that great at networking so I'd have to look up the specifics, but at a minimum I would suggest that you check your /etc/hosts file to see if there's a line like this:
127.0.0.1 your.dyndns.address localhost.localdomain localhost
Note that might have to reboot, or at least restart Linux networking for any changes you make to this file to take effect.