I'm sure Netgear had all the best intentions when they created a Wi-Fi Multimedia (WMM) setting, but the reality has been that it has acted as a Facebook blocking mechanism.  The pages would load, but none (or nearly none) of the imagery or videos would.  (Oddly enough, WMM is supposed to make videos a high priority.)

So if you have the symptom of your wired machines having no problem access sites like Facebook, but all of your wireless devices seem to hang on the media portions, check your Wi-Fi settings for WMM or other similar QoS (Quality of Service) settings that may be interfering.