Dry Glove Liners

[ballfrog]

Cold hands can be a sign that your body and head aren't warm enough.  When your core starts to drop, perepheral circulation slows down in an attempt to conserve the core warmth.  The opposite happens if your core is too warm, the arteries open up and try to flush the heat.  So, if you can keep the core warm but not sweat profusely, the hands benefit by becoming the body's radiator.

Try adding a layer of core warmth or stick a couple warmers in your pockets and see if that helps. 

It could also be that you have a strong Mamillian Diving Reflex.  Cold water to the forehead prompts the body to shunt blood to the core to conserve oxygen and protect the vitals.  Make sure your head stays as warm as you can keep it.

I also have cold hands, and these tips helped me more than double the time I can tolerate in water in the 40's.