I have multiple netflix clients and have never had problems, until ATV:
Wireless: WII, iPad, iPhone
Wired: desktop browser, Tivo, ATV2
Out of the box, the ATV would navigate the Netflix menus without a problem; but would not stream anything. I even plugged the ATV directly into the DSL modem, with the same results. I tried changing the DNS to 8.8.8.8, and that had no affect. I finally changed the DNS to match the DNS in my DSL modem
*-- that fixed the problem completely

*
The next day I reset the DNS and went back to DHCP; and it still worked. In fact, it worked everywhere were it would not before.