I have this issue of getting a cramp that puts me out of my commute for a few days - should be longer, but cant keep myself from riding. I just wonder if it could be a factor of the bike not fitting properly. Ive gone to the lbs that I purchased from and had a fitting. They told me that I fit just fine. However, why do I have this recurring cramp? I have a Bianchi road bike at 53cm Im 5'10, it feels fine, but could it be a factor of not enough leg extention at the bottom of the peddling that puts continuous pressure on the back of the calf from a bent leg? thanks

Do you do any leg stretches before riding? One is stand about three feet away from a wall and lean forward as far as you can with your feet flat on the ground. Hold the position for about 30 seconds or so. Repeat the process several times until you feel the muscles loosening. This will stretch your upper claves. To stretch the lower calves, bend your knees while leaning against the wall.
The problem you've described has never happened to me on a bike. But you don't want too much leg extension on the pedals. There MUST be a little bend to the knee at the bottom of the stroke.
Hope you figure it out.

thanks for the tip on both types of stretches. I cant say Im faithful to stretching, but I have been over the last few days with this problem, I will continue to stretch before and after rides.