Apparently Nikon either replaced or serviced parts (rings) on the lens connection (coupling) mechanism. Charlene also tried different memory cards. She says that the problem occurs after the camera has taken about 50 photos or so. It would seem to be a heat related problem. If she allows the camera to "cool" down for a while then it works fine for a short duration and then the error occurs again.
She primarily uses two lenses; a Nikon 50MM 1.8 and a Nikon 24-70 MM 2.8; the problem occurs with both lenses. The same lenses work fine on her Nikon D300. The flash hot shoe mechanism was also replaced (not sure whether this was considered relevant to this specific problem or not). Charlene uses a mixture of SanDisk and Transcend memory cards; she even purchased new ones in order to diagnose the problem.
Not sure whether Nikon managed to reproduce the problem or not.
'Since the mathematicians have invaded the theory of relativity, I do not understand it myself anymore' - Albert Einstein ‘I did not invent chimping, I just perfected it.' :-)