Since I started playing with my RasPi I've noticed that wifi for the whole house seems to stop working some hours after the Pi has been connected. My wifi comes from (with) a DSL modem with Frontier branded on the box. My iMac is two feet from the modem and is wired to it by ethernet cable. Everything else, iPhones, iPad and of course, the Pi used wifi. After the tenth (or so) time I had to power cycle the DSL to get wifi working again I decided to pull the USB wifi dongle out of the Pi and replace it with ethernet wire to that same modem. Guess what? 'Haven't had a wifi failure since. BTW: I had tried two different wifi dongles with the Pi.
Anyway, this is irritating. Especially since I'm planning a Pi application that depends on reliable wifi. I had two dongles to try but I lack an alternate wifi access point to experiment on. There is a lot of noise on the Web about dongle configuration problems (I had none) but nothing I've found about the Pi locking things up.