Did you do something like accept a driver from Microsoft or not notice Norton/Kapersky expire?
There are dozens of reasons for this to fail, including the WiFi card has failed. Sometimes it's a hijacked WiFi spot. Did you try this at other locations?
My laptop ( Lenovo Model No. 2049, 3000 G410 series) was earlier never connected to a wifi network. Recently when it was tried to connect it was not possible. Someone suggested that the wifi driver might have not been installed.. Searched in google and found the following three options matching to the laptop model - (1) Broadcam wireless LAN driver (2) Intel wireless LAN driver and (3) Intel pro/wireless 3945 ABG LAN driver.
Now, which one shd. I downloaand install and is this sufficient or if anything else is required to be done for the wifi connection in the laptop..