It is possible that this particular Wi-Fi network is malfunctioning at this moment.
Try disconnecting from it:
Open wefi client by clicking the wefi icon on your taskbar (if wefi is not running use the start menu to open wefi). You will see a list of all available Wi-Fi networks in the vicinity.
Right-click on the name of the network you want to disconnect from.
Then right-click on the name of the network again and select "remove from my favorites."
Go to Settings -> Wireless and Networks -> Wi-Fi Settings.
Select the network you are currently on, and press "Forget."
Alternatively, you can just switch Wi-Fi Off in the same screen.