I have several 360's that were in and out of RROD, when I fixed another one, I would swap my hard drive to the one I would be using and re-enable netflix on that one. You have to enter the code on the computer again and it should be working in a few seconds. The subscription is linked to your gamertag so the only way I know to do it is put your HDD in their system. You will have to do the code thing again when you use netflix on your system again.
I finally just swapped netflix to my PS3, the 360's finally crapped out totally. I may get a new gen 250GB soon I haven't decided yet.