Warning gona geek out on ya.
On most devices that run on the 2.4ghz frequency they run in 8ms bursts with 8ms rest, wifi normally runs in 16ms burst and 8 or 16ms rest, i believe. When the two are running the 8ms burst of the other devices cuts out 8ms of the transmisions on the airport. the interface robustness figures out when to send out 8ms burst to not get cut out.
and yes microwaves do have to do with it. Microwave ovens your wificard, wireless router, wireless phones, all run on microwaves, just at diffrent strength.