It's definitely a circulation problem, from crushing that large blood vessel in the perineum. If you crush it too much, for too long a time, it does get to be permanent. Not good.

The Terry Fly solved my problem. Every one's different. Bike shorts having a pad with a low spot down the center help. Perfomance Elites were good, but I hear quality is not so good now. Getting out of the saddle for one minute in every 10 minutes (by the clock) helps really a lot. I don't have nearly as much trouble now as I had when I first started high mileage training, years ago. Maybe a change in musclulature?