In the OP's case it seems pretty obvious that the new saddle is suspicious... if it's not comfy, he's going to subconsciously try to lighten the pressure on his crotch... most likely by using his dominant calf. Presto, cramp-o.

I know something about cramps in long road races, since I get them pretty much every time. I've read everything I can find, tried endless formulations and the best I can tell you is that "Science" seems to think that cramps are not caused by dehydration or electrolytes... best correlation from plain old fatique, second best from plain old heat. This assuming bike fit is not the root cause.

I will testify that mustard packets and pickle juice seem to help... but not until the cramp is already started hard to say with scientific accuracy, just my experience.