Hi Chris,
Thanks for the reply. My situation is different that yours. There was no power to the camera at all. The problem went away after I took the battery grip off and reinserted it. I was wondering if the contacts may have been contaminated after not being removed and reinserted after two years. When you use the battery in the camera you are always removing and reinserting the battery for charging. Maybe that action is good maintenance for the contacts.
There can be microscopic corrosion where a insulating film builds up. You can't see it, but it gets wiped away from the spring action of contacts. The process of plating electrical contacts usually results in multiple layers, including one of electroless nickels under the final gold plating. The nickel plating is not porous and should stop corrosion, but sometimes the process fails.
My engineering lab used to sample contacts as new batches came into the company for proper thicknesses of the plating by very carefully sectioning and then polishing the contacts so the thickness could be measured. It was a extremely difficult process, so I managed to buy a Seiko x-ray fluorescence tool to measure the plating in a non destructive manner. Even very expensive Mil-Spec contacts sometimes were rejected for poor quality plating processes.
After all, when a missile or nuclear bomb is pulled out of X years in storage, it has to work, you may have only one chance. That was my first job in the lab, figuring out why the connector contact in a trigger circuit had high resistance when a periodic continuity test was done. It was impossible to determine for sure if the contact had the dry film on it because it had been handled and any film had been wiped away. It looked perfect and met all specs, we tried every possible means to find it, even a electron microscope could not find defects. My boss was very happy because our company had not done anything wrong. We did institute some additional checks, when something like that happens, you must show you are changing your process.