On my CD iMac whenever I boot the machine as soon as it gets to the desktop it says that none of my preferred networks are available and asks me if I want to connect to an unsecure one down the road. If I go into the wireless icon my access point is there and it connects straight away then. I've had this for ages now and its started to bug now. If I put my MacBook next to the iMac then the MacBook connects fine everytime and I always get full bars when they are connected so signal isn't an issue. Any ideas?