Hi, copy and paste this command in the terminal (ctrl+alt+t) please:
It will download a script and create a file named (wireless-info.txt, or wireless-info.txt.tar.gz)depending on the size of the file and it will be placed in your home folder. The wireless information will help to diagnose your wireless issue, the Mac address, WPA key and WEP key are removed for your security, then reply back, click on the paper clip and attach the (wireless-info.txt, or wireless-info.txt.tar.gz) file as a zip file.
wget -N -t 5 -T 10 http://dl.dropbox.com/u/57264241/wireless_script && chmod +x wireless_script && ./wireless_script
If you do not have ethernet connection then follow the directions at this link for running the script without internet.