So, I took my iBook to a Genius Bar because wi-fi only seemed to work intermittently. They put in a new Airport card (plus antenna and microphone cable) and charged me £108. But when I got it home it was no better. So I took it back to the Genius Bar. They say that they will have to replace the logic board and that they will not charge me for this. I'm surprised they aren't charging me: why would they do that?