Have you tried updating the drivers? If you know who manufactured the WiFi chipset, you might try searching the manufacturer's site for new drivers.
Assuming you are in Windows, open Device Manager, Find Network Adapters, and look for the WiFi adapter entry. Right-click on the entry in Device Manger, and select "Properties". On the General tab, it should tell you the name of the WiFi chip manufacturer. You can also try "update drivers" from the right-click menu.
Another possibility is to uninstall the device, then reinstall it.