Zephyr,
Ayermail2 made a good suggestion about moving the cleats a little. Also, are you biking in your mountain bike shoes? The soles on a road shoe are a lot stiffer than on a mtn bike shoe. That's because when mtn biking you occasionally have to get off and walk so a softer sole. On a road bike there's little or no walking and the stiffer sole of a road bike shoe may also help the numbness. Just a suggestion.