Ginny-I had cramps like that during one of my races.  Cleveland!  at first I felt like someone softly drew their finger tip up the back of my calf. Hmm.. that was odd I thought.  Then not so softly.  Then it was like someone reached in and pulled on the calf muscle such that my toes were forced down like my foot was pointed.  For a split second I tried stretching it up against a curb.  Ha! Piano string was still taut so no stretching allowed.  Eventually I could do more than shuffle but it took awhile.  At Cincinnati after the race I couldn't move.  I told Mike to meet me in the W staging area since I couldn't walk.  I think it's an Ohio thing.

Seriously, electrolytes do sound like the thing.  Those two races were ones that I know I either didn't drink enough or tried using more water.  I know that we are all different but for me I do take the electrolytes and hydration seriously.  In this weather even for 5 mile run I make sure I have water with me.  Anything past that and I start putting Gatorade in the mix.  I will dilute but not 50% and when it's really hot where I know I'll be sweating buckets I don't dilute at all.  Then again, I've trained my stomach to accept the sugar part.  You can do Nuun or G2 which doesn't have sugar but I find that they make my stomach acidy.  I've also added Nuun tablets to Gatorade on hot long trail runs to have extra electrolytes.  That's just me though but I don't really cramp up as long as I drink electrolyte filled drink.