I have a 2GHz dual core MacBook, purchased in August 2006. For years airport functioned perfectly with no problems but recently the signal began droppiong from 5 bars to 2 and then to none. Once this happens my network no longer appears in the list of available networks, in fact sometimes no networks are available. The only way to fix the problem is to turn off airport and turn it back on again. Sometimes this doesn't work and I have to restart the machine or sometimes closing the lip for 5 mins and re-opening works. There doesn't seem to be an exact pattern. It occurs every 30 mins to 2 hours and nothing I've tried so far works. I've tried 3 dirfferent routers all with the same problem, annoyingly my girlfriends cheap Windows netbook works perfectly on all of them. I've tired altering the channels, changing from WPA to WEP, turning off the security, resetting the PRAM and removing and re-adding the router to my preferred network list. NONE of these solutions have any effect.
I was considering buying a new Macbook since mine is pushing 5 years old, but apart from this issue it's in perfect working order and since people with 2011 MBPs are having the same issue there's no point.
PLEASE APPLE or somebody can you help, this is driving me crazy and rendering my MB almost useless.