As far as a resourcepack fix, that isn't possible at the moment as the path that IC2 is currently looking for is /armor/ic2/texture/armor you can add that pat to your resource pack all day long and it wont mater since you have to put it all in the assest folder first or minecraft wont see it at all. and since IC2 isn't looking in the asset folder for its armor or Iron Furnace textures then it cant find them. And the iron furnace path is suppose to be directed at the Mincraft furnace GUI texture, but again it is looking for the texturepack path instead of the resourcepack path so again cannt be found, I am sure the mod devs know of the issue and how to fix it we just have to be patient and wait for the update, currently the 401 build has a few other issues but some of those are due to the mod dependent APIs not having been updated at the time of release, such as BuildCraft changing the name of the Water proof pipes to Fluid Pipes, so now IC2 wont recognize them either, but it will all get fixed as the other APIs get updated.