Have you checked your full IP address configuration on your machine?
If you have another machine that is connected to the same network with a functional network / Internet connection, compare the IP address configuration information on both machines. By running the following command on both machines:
Make sure that one of the malfunctioning machine is not configured with an APIPA address, this will almost always result in Limited or No Connectivity.
Refer to this post about troubleshooting APIPA addresses and Limited or No Connectivity issues:http://www.bleepingcomputer.com/forums/t/133029/ip-address-problem/
If you discover that you are working with an APIPA address which is affecting network connectivity via the USB WiFi adapter, you can switch the device from a DHCP (Automatically assigned) IP address to a Static (Manually configured) IP address and test connectivity. There are instructions on how to do so in the post above or the following post as well:http://www.bleepingcomputer.com/forums/t/133791/ip-address-conflict/
Research it and post feedback for additional advice.