Tony,

Just checking in to see if you found any resolution. Looks like you tried the only other thing I've done in the past. I used to have to shoot my old Minolta 7xi with a handwarmer rubberbanded to the body by the battery but I see you tried that. You know back in the day I was an electronic tech in the Army. Sometimes a bad solder joint would fail in extreme cold as the metal contracted. I'd keep pushing Nikon for resolution on these. I can't count the number of times we fixed devices just be reflowing the solder on circuit cards or connectors. Heck, even in my current job with a defense contractor we utilize environmental chambers to test devices for all kinds of conditions.

As I mentioned before, my 30D handled -20 for hours last winter shooting birds and such. I was actually a bit surprised at how well the one battery (no grip then) held up. Any problems I had were related to me breathing onto the frozen body. In fact on at least two occasions the rear thumb wheel went out from my breathing on them. This caused problems for me in adjusting exposure compensation.

I don't know much about Nikons but is it possible to power them via an external battery pack that could be kept warm inside a jacket? I know that can be restrictive but it's just an idea. One other thought, if you are using a grip with both of them is the performance better without it? Even though we would expect the grips to perform better with dual batteries (assuming they are like my Canon's) maybe the grips are failing in the cold, not the bodies themselves. My 30D's grip seems much lighter in contruction than the actual body and maybe they just don't insulate the battery as well, just a thought.

Jim