I'm so excited to read your post.
I have a book that concentrates on magnesium, and it says that we have way too much calcium intake here in the US.
We need more magnesium than calcium... else headaches and bone spurs (I forget what else) may result.
the author of the book wrote that in other countries where they take less calcium they also have less LESS osteoporosis because their intake of calcium and magnesium is better balanced than here. (No dairy lobby there, I expect.)
I'm SOOOOOO glad your cramp is gone!!!!
It also helps, sometimes to take the magnesium with vitamin C, since it needs a bit of acid to be better absorbed.
I take magnesium for headaches, now. It works great.