Original post by: Majesty ,
It can be either one. The only way to effectively isolate the problem would be to test the Mac with another known working Airport Card. I would start by taking the topcase off with a guide here and try re-seating the Antennae connectors to the card itself. Some have reported better connectivity by switching the antennae's positions on the card itself. If you are willing to try that you can isolate the issue.