What would cause a white stool?

Not normal. White stool is usually caused by a lack of bile which is secreted by the gallbladder. It needs to be evaluated by your physician.
White stool. Stools can be of different color by one's intake. Alot of antacids or a recent barium test could possible be a cause. However if this persists liver disorders need to be ruled out. A white (or clay colored stool) can signify lack of bile salts and an underlying liver condition. I would take this seriously and see your pcp asap.

Related Questions

What would cause yellow/white foamy stools? Also having lots of gas. Stomach making lots of noises. But no severe pain.

Flora off balance. Could be that your gut bacterial flora is off balance. Try taking acidophilus supplements for a few weeks to see if this restores it. If not better, see MD for some bloodwork. If the stools are hard to flush down, then they are rich in fat which can mean the pancreatic, bile system is off.