If you go to Start then Run, type 'CMD' (without the apostrophes), and enter:
ipconfig /all
Command prompt will list the status of your network connections, and adapters. If the adapters are enabled, it's possible the setting to use a third-party wireless assistant has been disabled. You can check for wireless networks by going to Start, then Connect To and select Show All Connections. Right click the connection you use for your wireless, and select View Available Wireless Networks, it may list your network there, in which case you should be able to connect.
If you're certain that the wireless switch is on, it's possible something could have been altered. If you have changed anything recently, revert it back, to see if there's a difference with your wireless connection.
When you try to open your third-party wireless configuration program, does it return an error?
