hey, i've had problems with this sort of tightness too. Here's what I can suggest.
1) drink a lot of water, and eat a lot of bananas.
2) definitely try to get a massage on your calves; if you cant get someone else to massage them, use your opposite kneecap to massage and to get some blood flowing through the muscles.
3) --- This may be the most important. It seems as though my own lower-leg tightness was brought on by beginning runs simply too fast. I would suggest you find a nice soft place to run for approx 10 minutes VERY VERY easily. I'm talking maybe like a jog. you dont want to have any sense of forcing anything. you'll know how you feel after maybe 15 minutes.
4) Ice after running, and make stretching your lower legs a habit. It seems to help me, at least.
Basically, I've been a little stuck with similar problems as you. I'm really not sure if its compartment syndrom, overworked calves, or whatever, but the above has definitely helped.
anyway, good luck. be diligent in taking care of yourself!