in 14.04 USB wireless adapters based on the RT5572 chip (148f:5572) are covered by the rt2800usb kernel driver...
If you know it works in 14.04 (or its vendor:product ID string matches 148f:5572), you could install the LTS Enablement Stack for 12.04 which should bring you current installation up to the 3.13 kernel (as used in 14.04)
If you're 100% sure you're running 12.04, open a terminal and run:
sudo apt-get install --install-recommends linux-generic-lts-trusty xserver-xorg-lts-trusty libgl1-mesa-glx-lts-trusty
when that's finished, REBOOT.
Once rebooted, run:
to make sure you're on the 3.13 kernel.
if that doesn't automagically sort out the driver, please post the output from: