Give the eggs 12-24 hours. Usually by a few hours, I had observed some eggs going white when I bred angelfish. What fish are we dealing with?
Did you treat the egg's with some type of antifungal agent (maraxoy, methal blue or hydrogen peroxide, etc...)? White eggs are either infertile or have gotten fungus. Also, are you sure you have a male and a female? Most Chiclid eggs will hatch within 2 to 3 days depending on temp.