I've been keeping an eye on this thread, because in this one or another I saw that there was a firmware update available that I hadn't installed. After I did, I started having a ton of issues getting and staying connected to the NT-505.
My setup is a little different than most in that I have mine connected wirelessly, using a Wireless Access Point configured as a client and then connecting that to a four port switch that I have the NT-505, my Oppo BD player, my TV, and my Roku connected to. I've been having some issues with my router (waiting for a replacement) and thought that might be the issue.
I removed the switch and connected the NT-505 directly to the WAP and it seems to be functioning without any issues for about a day now. I really like mine, but it's troubling to hear of so many issues. I'm hoping the new router and a new WAP will fix my issues. It did work OK when I ran a long ethernet cable directly from my router, so it may be that it's an issue with my home network. I was also having issues streaming Netflix on the Roku, so I'm not convinced it's a problem with my NT-505 yet.