I encountered problems with my Wireless adaptor Edimax EW7711Uan on Ubuntu 12.04. I was able to get list of available networks, but couldn’t connect to any of them. I thought there were a driver problem. After searching for this issue, I tried some commands to solve it but these solutions didn’t work for me. Then i found this link: http://ubuntuforums.org/showthread.php?t=1342593.I learned that two drivers were interfering with each other that i had to blacklist one of them.
I opened blacklist file with ‘sudo gedit /etc/modprobe.d/blacklist.conf’ command. Then i added ‘blacklist rt2870sta’ line at the end of file. I disconnected my device and connected again. In seconds i established internet connection. You can read further information from link on ubuntuforums here that i pasted earlier.
Happy linuxing & sırfing.