Nu tak jsem našel další návod, ale je trošku komplikovanější -

Download new driver from ralink support page (version 2.4.1) and unpack it somewhere (I did it in my Download folder).
Read README_STA_PCI file - find file config.mk in os/linux folder, open it with gedit and edit lines: -
HAS_ATE=y (originally was n) -
HAS_WPA_SUPPLICANT=y (originally was n) -
HAS_NATIVE_WPA_SUPPLICANT_SUPPORT=y (originally was n) and -
HAS_ANTENNA_DIVERSITY_SUPPORT=y originally was n)

Now, before compile, install via synaptic these packages: build-essential, devscripts and cdbs. * Note : I didn't have to do this, but perhaps you can try it out if you have your wired internet working. Edit is mine, not Rtomakov's. *

Enter DPO_... folder from terminal and do sudo make, and after make finishes (without errors, ignore warnings) do sudo make install. That is it, but it is not over yet. Now open /etc/modprobe.d/blacklist.conf (as root) and add at the end: blacklist rt2800pci. Also open (as root) file /etc/modules and add: rt3390sta.

* to do the above, i used the command - gksudo gedit /etc/modprobe.d/blacklist.conf and - gksudo gedit /etc/modules. Make your edits in gedit, Save them and CLOSE the file to return to the terminal.*

Now, reboot. That should work.