I have these ALL the time! I have fallen arches and back problems!
Try this when a cramp comes on, it looks silly but it works 100% of the time for me! Kneel down on the ground, but with the balls of your feet still flat on the ground behind you, so that your heels are up in the air and you're effectively sitting on them. Don't do it too fast or you might pull the muscle thats on the very inner edge of your foot.
Just like this picture:
http://www.digitalrunning.com/wp-con...otstretch2.jpg
I can actually induce foot-arch cramps...not that I want to...that's how sensitive my feet are. They're usually induced by repetitive movements of my feet when trying to stabilize the rest of my body (when standing on one foot, doing kickboxing that requires me to be bouncing on the balls of my feet, jump-roping, running). The great news is that now that I'm running 5 times a week, I haven't had a foot cramp from running in I don't know how long...ages! I can still get them from doing other odd things, but it leads me to believe that once you start using your foot in such a way that it's not used to being used, you build up that muscle and eventually the cramps will stop!