Calf cramps anyone?

I actually used to have the same problem and my solution was neither hydration or nutrition related.  In fact, it was my shoes.  I used to run in Nike shoes that had NO support, especially for pronation (foot rolling inward).  I found that simply by changing to shoes that offered better support, Asics in my case, my calf problems went away overnight!!

Now I'm not saying you have the same problem, but I think you should definately take a look at the shoes you're wearing and if they are suited to you.  Trust me, it can make a HUGE difference. 

IF you are certain you are properly hydrated and IF you are certain you have the proper nutrition/electrolytes then the next thing I would do is try to isolate the problem.  I don't think you stated in your post whether this happens if you just run without doing the elliptical first.  Try that and see if it happens.  If it does happen, and it's around the same time in to the workout, then the likelihood that it's the shoes goes up.  If it happens but it's later in the workout then it may be more nutrition/hydration related than you think.  Is it possible that it's happening at a certain TIME in your workout, you just always happen to be running when it occurs?  If it doesn't happen at all when you run without the elliptical (and your workout is long enough to test for the time problem mentioned above) then it may be your body is not responding well to the stress of running immediately after being worked on the elliptical and I would separate the workouts to try to prevent injury.  It may be (and I'm theorizing on a lot of this without the credentials to back it up) that since your muscles aren't properly developed yet, when you are doing the elliptical and then begin running they aren't able to handle the change in workload.  I waited several months to begin brick workouts for just this reason.

Then again, I could just be full of b.s.  Maybe someone with actual knowledge will chime in on my theory.  If nothing else, I'd stick to one excersize per workout for a while (leg related) and see if that helps.  Good luck.