According to the Insight book and a 1986 Awake article, C-14 dating is reliable for all dates SINCE the flood (2370 BCE or so). Supposedly the deluge changed the atmosphere so much, letting in a lot of extra radiation, etc., there's no way of knowing how much carbon was in the atmosphere prior to that event, so all C-14 dates purporting to be EARLIER than the flood are unreliable.
This flies in the face of all kinds of evidence, the biggest being that if there were such a sharp delineation between pre and post flood dating results, it would be easy to see and highly obvious to the scientific community. And, of course, this assumes there was a literal global flood, an occurrence for which there is ZERO evidence and, in fact, a boatload (no pun intended) of evidence to the contrary.