Based on the information at hand, right now, from this thread and other sources of information, here is what I think to be an (unofficial!) "best practices" troubleshooting guide if your AppleTV will not play Netflix (or other) streaming video wirelessly as you expect it to :
1. Cycle the power on your AppleTV. Just unplug it from electricity and wait a minimum of 30 seconds before applying power again. Check to see if the problem continues, or not.
2. Power down your entire network, including the AppleTV. This includes your router and your cable modem / DSL router. Again, give it a minimum of 30 seconds without power before plugging anything in. Apply power again in the following order : cable/DSL, router, AppleTV. Check to see if the problem continues.
3. Unplug everything from your network and run a data cable from your cable modem / DSL router directly to your AppleTV so the AppleTV is the only device on your network and see if the problem persists. This is now the baseline for testing. If the AppleTV works, there is a high probability something was interfering with your network or the router was misconfigured in some fashion.
4. Write down or otherwise record all the settings you can find from your router AND your AppleTV. This is a good practice no matter what. Before you go on make sure you have - by paper or text file or screen shot - recorded ALL the settings of your router AND AppleTV. *DO NOT PROCEED IF YOU HAVE NOT BACKED UP BOTH SETS OF SETTINGS*. You have been warned.
5. On the internet, search for the reset instructions from the manufacturer of your router. Do a 'hard' reset, taking the router back to factory settings. On some routers, there are two levels of reset : hard and soft. For example, on some Linksys routers holding the reset button for 5 seconds will give you a non-volitile (you won't lose settings) 'soft' reset, while holding the same button for 10-12 seconds will give you a 'hard' (all your settings are wiped out) reset. Perform the hard reset on your router, and also reset your AppleTV back to factory settings.
6. Wait for your router to fully restart from the resetting sequence. Without changing any data, or altering any settings anywhere, attempt to connect your AppleTV to the router using the default settings for both the router and AppleTV. Test for correct operation of Netflix or another streaming service you were having trouble with.
7. If all the preceding steps have failed, try taking the AppleTV to another location and testing operation with that wireless network. If your AppleTV works at another location, but doesn't work at your location, I am 99% certain the problem is your router. I suspect, but cannot prove right now, there may be an incompatibility problem between the AppleTV and certain routers. At this point, I believe this is what is making people believe this is an Apple or Netflix problem. I also note this is not a high improbability as there are compatibility issues with AppleTV and certain HDTVs.
*It would be very helpful if those who are having wireless connection issues where they cannot stream Netflix or other video with an AppleTV to post the brand, model numbers, and software/firmware version numbers of their routers to see if there is any correlation to be had there.*
8. If you are able and comfortable with changing the settings on your router, try taking it manually to a "B" connection instead of letting it auto-select between A, B, G, and N. Test the Netflix streaming on your AppleTV to see if it works.
9. Re-enter all the settings of your router, paying particular attention to re-entering them correctly. Do so with your AppleTV as well. Try the Netflix streaming again, and if it does not work
immediately run a speed test from speedtest.net, and pick closest server to you. If your bandwidth is not running over 1.5mb/second, there isn't anything anyone can really do for you. As I stated in another post, for optimal performance and quality that 1.5mb/second limit should be treated as concrete, not jello. In other words, no - there is no 'fudge factor' to that limitation. It really is the absolute minimum for correct function.
10. Please call Netflix. If nothing has worked so far, and streaming from the Apple Store is working correctly, there is a high probability that it may be your Netflix account. Netflix would really like to hear from you no matter the device you are having trouble with. They really, sincerely want to get to the bottom of this so every AppleTV / Netflix experience is a great one. Repeating once more : Netflix can't fix what they don't know about, so please, please, please call Netflix even if you are somehow sure it is all Apple's fault. Netflix can use all the data they can get to find a solution.
11. Call Apple. The same reasoning applies here, too. Apple would like to get to the bottom of this if it truly is their product that is defective, but they can't prove that without your help in supplying them with data. Following these steps is a great start to doing that, so long as you do them before you call.
These steps are NOT meant to be all-encompassing. This is just a 'launching pad' for other troubleshooting steps. You should still check all your wires, cables, et cetera. Nothing I have written here obviates the need for troubleshooting steps like that. These are just the first line of defense, as it were, and not meant to be the entire process.
But I will also repeat : *PLEASE, PLEASE, PLEASE DO US ALL A FAVOR : DO NOT CHANGE MORE THAN ONE THING AT A TIME IN YOUR TROUBLESHOOTING, AND PLEASE OBSERVE ANY AND ALL CHANGES FOR THE BETTER OR WORSE BEFORE YOU JUMP TO THE CONCLUSION THIS PROBLEM IS ANY COMPANY'S FAULT.*
I am open to believing the AppleTV has a fault, but I will not go there without iron-clad proof to offer up to Apple so the problem will be permanently fixed. Everything posted here that doesn't move us forward is just noise, and I beg you : please let's keep the noise to a minimum until we have a solution.