Back in September of 2011, researchers at the Gran Sasso National Laboratory in Italy observed some incredible results in their OPERA (Oscillation Project with Emulsion tRacking Apparatus) experiment. It seemed that elementary particles known as neutrinos could travel faster than the speed of light.
The researchers were shocked by these results. If the speed of these particles did in fact exceed the speed of light, then fundamental laws of physics would be contradicted. Specifically, this conflict's with Einstein's theory of relativity, which conjectures that no particle could move faster than the speed of light in a vacuum. Many current understandings in physics are based upon this theory. Thus, if Einstein's theory is inaccurate, then so would be those theories which rely on it. This article in Nature describes the gravity of the situation (haw, haw).
But, as it turned out, the astonishing results were actually a result of flawed hardware. Apparently, a misplaced fiber optic cable was responsible for showing results that suggested that neutrinos may travel faster than the speed of light. Once the researchers adjusted the cable, it became clear that the neutrinos were in fact traveling under the speed of light (but only just). [sources 1, 2]
This mishap is not alone in the sense that false results lead to a conclusion which was majorly hyped and publicized. In research, when results are groundbreaking, one should always adhere to the scientific proverb, "more research is necessary," before stating anything definitive.