Excellent article on Radio Frequency (RF) Interference:
Like a noisy engine in the background of an audio recording, radio-frequency ¬interference is the result of a device ¬"listening" for one signal at a specific frequency and "hearing" another. The 2.4-GHz microwave overpowers the 2.4-GHz router and the laptop gets ¬confused.
Preventing Radio-Frequency Interference - Wireless Bandwidth Spectrum - Popular Mechanics