I just wanted to throw this out there for anyone else that may find this thread in their Google search.
If you have a static IP set for your DNS-323, ensure that it is a high enough IP. With all of the devices floating around our houses today which connect to our networks (PS3, mobile phones, tablets, etc.), you will need to make sure that there is no cross-over.
Example: If the power goes out. Network resets. Your devices begin connecting to your network. If your DNS-323 static IP is low enough, you might have another device connect to the network faster and take over the same static IP. This will cause the DNS-323 to show up/be accessible, but then disappear minutes later.