I find to have the same issue as described by Leon.
Problem is, I tried to reopen my iMac, but it won't open the front bezel with the card trick..
So I opened it from the bottem and undid the EMI shield. It appears there's only one antenna attached to my airport card.
does anyone know if this is normal, or should it always have two antenna's?
Is there a way to fix this? Maybe by creating my own antenna somehow?
Thanks!