I have had the same issue in approximately the last month with my Netflix account needing to be re-activated 2 times. I have not changed my account or any details since receiving the box several months ago. I have been very pleased with the ease of use of the box and it works very well other than I have seen this issue as well at least two times.
After 4 months of nearly flawless use, I've had to re-activate my Roku twice - 2 weeks ago, and again this morning.
It's an annoyance, but I wonder if it means that there's a technical problem at the Netflix server or some other difficulty with the Roku keeping the connection "alive".
Either way, Roku/Netflix should send out a system message or e-mail about any known issues or downtime.
Just off phone with Roku/Netflix. Can't find any problem on their end, though the Netflix tech sez sometimes when the DHCP lease is renewed, something there leads it to deactivate the device. I guess that could have happened. The Roku wasn't used for a few days there until the DVDs started drying up.
He sez they can activate them by phone as long as you can get a new activation code on the TV end (which I couldn't).
Trouble is, my phone and internet go through the same modem...I can restart the router any time I want but if I have to restart the cable modem then I lose the phone call AND the internet. Arrrggghhh. Glad they didn't tell me to try that.
So I'll call from the cell next time and allow for restart of all networking components without going completely incomunicado.
I had to reactivate my Xbox on it last week to. Oh on a side note. I have vonage for my phone. Working with time warner on a problem, while talking to them, they rebooted my modem. When it came back up, I was still on the call. Go figure that one out lol.