bro i need to know the type of wireless card u use , before that have u checked your restricted driver manager , Ubuntu has a restricted Driver manager wh contains those driver in your system that are not open source and as such are disabled by default , but u can enable them and ubuntu would if necessary download the necessary driver needed, to check your restricted driver , go to system/administration/restricted driver manager , in your top- panel, u will see all the drivers that are not open source on your system , to enbale them u have to check them
look at mine u can see that i have checked my two restricted drivers which in my case are my nvidia cards and my intel wireless card
Damn! i have being banned for uploading images

edit
*ok i found a way around the ban

anyway just check your restricted driver and tell me what gives,
if that doesnt help , tell me the type of wireless card your system is running and u can find that under System/Preference/Hardware Information scroll through to your wireless card
good luck