Since September, scientists have been scratching their head over results that appear to show neutrinos traveling between Switzerland and Italy faster than light would. . . . there was a good reason the measurements and reality weren't lining up: a loose fiber optic cable was causing one of the atomic clocks used to time the neutrinos' flight to produce spurious results. If the report is confirmed (right now, there's only one source), then it provides a simple explanation for the fascinating-yet-difficult-to-accept results. According to the new report, researchers are preparing to gather new data with the clocks properly hooked into computers, which should definitively indicate whether the loose connection was at fault.
From here via Gauge Connection.
Just to recall the situation, the initial report has shown neutrinos travelling at speeds a detectable, but tiny percentage rate in excess of the best measured values of the speed of light, when special relativity and what we know about the kinetic energy of the neutrinos and their rest masses would have caused us to expect them to travel at speeds below the speed of light by an amount too small to be experimentally detectable.
Everyone in the physics community had suspsected as a most likely explanation experimental error, which appears to have been the cause of the superluminal speeds detected, to be at fault, but until no, no one had been able to point to a source of experimental error that would create a discrepency sufficiently large to explain the result.
A variety of theoretical explanations for variations of the theory of special relativity had been advanced to explain it (I myself viewed the possibility that the measured speed of light is actually slightly lower than the true value of "c" in the equations of general and special relativity due to interactions with electromagnetic phenomena unaccounted for previously in the vicinity of massive bodies of ordinary matter, i.e. an error in past rather than current experiments, as most likely if the experimental result from OPERA were confirmed). But, it turns out that those theoretical explanations will end up being disfavored going forward since their prediction that indeed OPERA could be seeing superluminal neutrinos didn't turn out to be accurate.