I am also experiencing this problem but what amaze me is that it only occurs when i try to use my laptop in our office. In other places, i can use my laptop without a problem. By the way, i am using an ASUS W1. There are secured and unsecured wifi access in our area and this problem started when i tried to use the unsecured wifi network once when our secured wifi was down.
More aboutequal problem
Try to reinstall / update your WiFi drivers. See if that solves the issue.