The first item I thought of when I started reading your query were the contacts in the camera: Are they all properly in place and free of oxidation or contaminants? Then I read that you had already taken the camera to a repair shop and they couldn't find anything. Since I believe they *should* have checked and cleaned the camera contacts as one of their first attempts to troubleshoot the problem, I sure wouldn't have much faith in that particular repair facility any longer. As already mentioned in another response, apparently there are no Nikon authorized repair shops in St. Petersburg, FL but, even so, after hearing your description of the problem any repair facility should check the electrical contacts for oxidation or contamination whether they are authorized by Nikon or not. They had your camera for three weeks and found nothing and you fixed the problem by using the first recommendation you got from Nikonians -- not a great performance by the repair shop.
Glad to hear the Deoxit worked for you and your camera is back in working order.