I have 10 AirPort Extremes Base Stations (4th generation: A1354 MC340LL/A) that seem to "drop off" on occasion. Power seems to keep (green led stays lit), does not seem to loose connection to switch (switch port light stays lit), clients/users appear to stay connected to the AP (their wireless connection to the AP maintains).However, the client/user looses throughput and has the symptom that that they can not connect to any web/network destination. This drop seems to either repair itself within 30-60 seconds or the end user can re-establish a connection by turning off/on wireless (although I am thinking the time it takes to re-establish takes about the same time so not confident that it actually fixes the issue). Also, you can watch using AirPort Utility that some of the APs will drop out and then reappear. It can be one at a random time, or a bunch all at once with no seemingly set pattern.This dropping occurs with both Mac and Win clients. I have replaced switching and we have a new modem and service. I have changed from Auto to Manual channel for both the 2.4 and 5 GHz and set the Radio Mode to specific (a/n & b/g instead of auto). The APs have a static IP and have that IP range reserved so should not be any IP conflict.Any thoughts??? Better yet, anyone have a similar experience and how did you overcome the issue?Thanks in advance.