bad circulation is simply bad circulation. hell, my toes are freezing at the moment while I'm sitting here and its almost 70º.
Good footbeds, proper fit, thin socks are all good steps. One little trick I tried climbing that worked somewhat well for skiing was to take some of that solar emergency sleeping bag material, and cut it out in the shape of the base of your footbeds, and then use a spray adhesive to attach it. Might not work at all with some customs though, but it does a decent job retaining some of your heat.