Muscle Problems

First my neck, now my left calf.  On Tuesday, after a good workout on my indoor bicycle trainer, I was standing at the kitchen sink and my neck seized up.  I went from perfectly fine to having an immobilized neck in a flash.  The pain was incredible.  I could barely move my head.  Jack massaged my neck for the next few nights and I applied a hot pad the second and third night, and it seemed fine.  After two days off from exercise I hit it hard again at my Big Spin class.  After about 70 minutes of spinning we headed to the pool.  I was fine until the very end when we had a 4 person relay.  When it was my turn to swim and I pushed off the wall, my left calf seized up in a massive cramp.  I swam the lap with my leg dragging behind me.  It relaxed slightly before my next leg of the relay so that I could swim, but the calf is still painful.  I am guessing that I must have some sort of electrolyte imbalance or something.  I had a physical a couple of weeks ago and all of my blood work looked fine.  I may not be drinking enough water.  I am going to focus on drinking water, eating a variety of veggies, stretching, and trying to get this cramp worked out.  Any suggestions?