What sort of Powerlink cables are you using? They should be Mark 3 with the small triangle mark on the plugs. Beolab 3s are very sensitive to interference and the cables need to be the shielded ones.
From what you say though, I would suspect a fault in the Surround Sound module of the BV3. Have you tried connecting the speakers just to the BC2 to see if there is any static there? I would guess that it will be fine. If it is, I would suggest getting the module looked at. Is it still under warranty?
Welcome to Beoworld.