"Cosmic ray" = IT equivalent of "Gremlins", i.e. joking term for an unexplained failure and especially one caused by human factors.
I am not sure, but you would have to think for this to be published (Cosmic Rays) that it is designed to take the blame away from a nasty - potentially catastrophic software/hardware fault within the ADIRUs.
Yet surely, saying that the 330 is subject to random cosmic rays would have to be even less reassuring. If they had said the ADIRU can be replaced due 'this' (ie whatever fault they find) particular hardware fault, then most people would be satisfied - but now the whole jet can be susceptible to complete lack of control from unseen random cosmic rays! FFS...Really?
I can just imagine the punters now (or the random sandwhich shop worker interview) "I cant hop on an Q airbus again now due to cosmic rays"