I had been adding a small amount of soy protein to my drink mix for the second bottle on longer events. And I've been having constant cramping issues for the same amount of time. Being rather slow, it took me nearly two years to try it without. 5 hours into a road race in 90 degree heat and not one cramp.
Started talking to people who had the same type of issues, some of them were using another commercial product that had protein as their drink of choice. Checked the label. Soy.
No mas protien until I figure something else out. Whey protein gives me horrible gas and stomach issues, but no cramps.