I had 3 AirPort Extremes set up so that 1 was the main, and 2 others were extended. Everything worked perfectly with 7.5.2, but since updating the firmware to 7.6, the two "extenders" are dropping periodically and I have to power cycle them to show back up on my main AE. I haven't changed any settings, and I've tried changing configurations, resetting to factory defaults, etc. No luck. Basically if I unplug AE 2 and 3 and plug them back up, it'll register with the main (AE 1) router. If I power cycle the main router or after a period of time, AE 2 and 3 will drop the connection and must be power cycled again before they will connect to the network. As I mentioned before, everything was working perfectly prior to the firmware upgrade. Not sure why I even upgraded!