As above really, I get them quite severely if I increase mileage/intensity too quickly. I take a couple of weeks off running (does my cycling and swimming training the world of good anyway) and they go away, but it does interrupt my progress, and I have to start a little way back again.
I went to a sports physio who showed me how to self massage the area to break down the adhesions, and I do lots of stretching of calves and shins too.
I did a Duathlon on Saturday with a 12k run, 40k bike, 4k run and have had no pain whatsover from them either during or after. So treat them right and you will get over them.
I would say stop running now, do lots of stretching, and a bit of other low impact cardio if you want/can. You won’t lose any fitness, and could actually be very well rested and fresh for the day.
And good luck.
And post up your time.