Running too slow?

I don't know if this will help you or not but I'll tell you my experience. I can run for over an hour, my pulse stays around 160 (way high for my max, which is actually in the 150's), I feel fine and feel like I could go on forever. I'm not out of breath and I completely enjoy it. However, as soon as I slow down for my cool down, I have almost instant cramps in my calves. It is horribly painful so now I slow my jog down as slow as possible, then walk fast for 5 minutes, then walk slower for 5 more and so on, until my pulse is down to the 120's. I don't get why it hurts so bad when I slow down. It doesn't even make sense. The only thing that gets rid of it completely is to do the above and to make sure I stretch really well afterwards. I always warm up for 10 minutes by walking at about 3.5mph. Stretching BEFORE I run only makes it worse. I can't explain that either.

If I stretch before running then I can't run as far. <-- Truth!

Try not stretching before, and run. See if it makes a difference. Definitely stretch afterwards.

Also, make sure you eat well.

I agree. I cannot stretch beforehand or my legs tire quickly. I have to stretch after. Also, look at what you ate the night before. I find what I've eaten affects my ability to run. Junk food - not so good for energy.

On stretching: there is a lot of mixed advice out there, but my understanding of the exercise science research is that stretching doesn't do much for you, especially when done before exertion. Afterwards, go ahead and do it if it feels good. I do it for that reason.

I just remembered reading about a study that found a correlation between calf circumference and lower leg injuries. The upshot was that the stronger your calf muscles, the better. So consider adding some strengthening exercises to your routine--I do standing one-legged calf raises (stand on one foot, get up on your toes, then lower, then repeat). It's good for balance as well as strengthening the calf and various stabilizing muscles in your lower legs.

Shoes: they sometimes do not work out even if they are new. I have a pair right now that some people praise to the skies, but they gave me shin splints. If you are serious about running, you should consider picking up another pair--you'll need a new pair about every six months anyway (give or take, depending on how much you run).