Buddy,

You need to toggle the flag of wireless inside /etc/networking...Please search in net 

I had same issue and resolved.Below are some debugging links.Let me know if you can't resolve 

i can do more research for you.What is the name of your wireless card?driver?Is there a switch 

to turn it off and on did u tried that?

https://help.ubuntu.com/community/WifiDocs/WirelessTroubleShootingGuide