Thank you all for your suggestions and advice. I apologize for the delay in posting my thanks but we have since left London and have been exploring the Cotswolds with unfortunately sporadic internet service. However, here in Lower Slaughter (near Burton-on-the-Water)we seem to have some luck. Tomorrow its on to Stratford-on-Avon to pay our respects to the Bard and visit friends.
That said, my problem continues on an infrequent now-and-again basis. I am using Tamron lenses on this trip. The 24-70 and the 18-270. I will try the suggestions you've offered.
Brian: no I am not wearing Polarizing sunglasses. I've already learned that lesson the hard way!
I will try the lens mount check again. I already have removed and reseated the lens; I remember getting the "FeE" error with my D300s, so I'm aware of the need.
The other suggestions about the battery removal and etc. I will also try and,yes, I understand the need to each one by one to try and isolate the cause.
I will also post again later this week (while in Edinburgh) with the results. I thank you and the Nikonians again for your assistance.
One other off-topic question: I believe from my visiting this site that Martin Turner, one of the moderators, lives in the Stratford-on-Avon area. Am I correct in this assumption?