Check this thread: http://arduino.cc/forum/index.php/topic,98494.0.html. Similar issue, solved with a capacitor.
I tried connecting a 2200uF capacitor 5V>GND, but this did not solve the problem. I replicated the problem by plugging in a fridge, a microwave, and a water cooler into a power strip and then connecting the arduino usb to the other plug in the same outlet. When I flip the power strip on/off, the arduino eventually hangs and loses connection.This is a really annoying problem. :/
I think that is going a little far. You only need to simulate with the appliances that will be used there. (and the microwave does not use any energy when plugged in) I put my cap across the power supply output, not the 5V. Energy stored in a capacitor varies quadratically with voltage. My circuit ran for three days and never reset. Even if it does, I turned on the WDT for two seconds as a redundant safety measure.
UPDATE:I added a 220Ohm resistor from -cap->GND.... AND IT WORKS! no more surge problems!
220 between 5V and ground? Or somewhere else?
Interesting..so in series with the cap. That would limit the rate of charge and discharge to about 22mA max. I wonder why that fixes the problem.
Some large radio antenna on the nRF24
There are several reasons an Arduino might reset, one of them is power drop-out, but its not the only one.