What causes charlie horses in feet and only at night?
They are generally caused by mineral deficiency such as potassium and calcium, low levels of body fluids when performing strenuous exercises and also hormonal imbalance. You should check with your doctor and you can get more information here http://www.medicinenet.com/script/main/art.asp?articlekey=47633
I get those myself an I was told not drinking enough water. Since I started drinking more they have seemed to go away.
Muscle cramps generally are caused by overuse of the muscle or lack of calcium. Look at those two things as a possible cause of the cramps.
It also may be because you are not stretching enough, try stretch every night before you go to bed and drinking lots of water.