I remembered I had this problem some time ago on Ubuntu 9.04 and after wandering on several forums I got it working. From experience, this problem normally occurs when you power off you system abnormally :)
So many forums suggested different hacks but not close to the solution so they never got it working perfectly.
To solve this problem,
Simply run the command below:
$sudo rm /dev/rfkill
After that, simply reboot your computer
$sudo shutdown -r now
When you reboot the device /dev/rfkill deleted will be re-created automatically
and you should be able to connect back to your network.