I wasn't able to find Wendy's blog about soap in bed, so I will post this here in hopes she may see it.
I was having the same problem -- the soap appeared to stop working and I was getting night cramps in my feet and legs again. I decided to try something. Using a metal pot scratcher, I went over the whole bar vigorously, exposiing new soap. I haven't had any cramps since. It may just be a fluke, but if it works.......