If you read the sticky by Ursula at the top of this forum you'll find a link to the connection problems thread and other hints about how to find a solution.

Look also for posts by gbildson--he has another test and more ideas on this difficult problem.

Oh--if you do find out why your machine won't connect--do post back what works to help others. Most of us have no problems connecting, so it's hard to know what's going on.