Ubuntu 12.04 brightness problem Sony Vaio T13 ultrabook

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http://askubuntu.com – I recently installed Ubuntu 12.04 alongside Windows 7 in a Vaio T13 ultrabook. I cannot use the the Fn+f4 or Fn+f5 to change the brightness. The bubble appears indicating that brightness is being changed but with no visual impact on the screen. I've tried many solutions involving the manipulation of the /etc/default/grub file but none of them worked. Whenever I tried this manipulation the screen still didn't change, however the bubble stopped functioning properly. This is not a problem of the Fn shortcut. Even when I try to change it in the Brightness and Lock on System Settings, the bar do (HowTos)