I have 2 samples of logitech mx518 and they both whine. Not really loud, but some times i can single out the sound and clearly audible if held against the ear.
I actually opened one of my mx518:s to see if the whine could be cancelled, after some close listening i located the whining to the 2 left mouse button-click boxes, on the front PCB. There are two boxes very close to eachother, one for the left click and one for the center wheel click, it appears that theese 2 boxes cause the resonance, which is then amplified through the mouse plastic body.
Cancelling the whine whithout impeding on the clicking comfort prooved to be a huge challenge, i initially wrapped the boxes with electric tape which silenced them, but also disabled my left mouse button
After some trys i eventually settled for a lower amount of tape that muffled the sound slightly but did not remove it, to ensure that the mouse buttons work. The front button PBC is also attached to the mouse housing with a screw, I loosened this screw and put some tape under it which also helped a bit with resonance, but unfourtunatly i didnt find any way to kill the sound completely, while keeping the functionallity.
*sigh* Life of a silencer, when my PC finally was quite enough, after changing tons of components the freakin mouse starts to bother me