Prue Gore-Tex^® Waterproof Slip-On Sneaker (Women)

I had high hopes for these shoes, but the strangest-ever experience. They seem to fit well, except for pressing down a little on the big toe of my right foot, but every time I've worn them (at least a dozen times), I've had terrible foot cramps later. I thought maybe it was the insole pressing in odd places, so I took it out and put in others from shoes that fit well. Still, the cramping keeps happening--even waking me up in the middle of the night. I can't figure out what's wrong with these shoes. I love the looks and the fact they're waterproof, but now I'm afraid to wear them again.