Runners World has a great article about this common injury. There are a few things you can do to help prevent it:
-Where the right type of running shoes, and make sure they're not overused.
-Run on soft surfaces
-Wear a heel cushion or cup in all shoes you wear (running and every day shoes)
-Chose your every day shoes very carefully
-Use a night splint
-Stretch your calves before getting out of bed in the morning
-(mostly importantly) take care of your feet and calves
-Ice after running (during the winter time, this may be the most difficult thing to do, but so worth it)
-Take an oral anti-inflammatory
-Use shoe inserts
-Wear a night splint
-most importantly) See a Doctor!
I hope this helps and any problem, your Doctor can help you!
What injury are you suffering from?