reattaching hinge to cupboard?

The hinge has come off my cupboard. This is a cupboard (white laminate) that has a corner hinge to allow it to bend with a smaller connecting cupboard. The problem is that I can`t seem to screw the existing screws into the back of the cupboard because the material is hard and the previous holes that were there I filled with wood filler but the screws keep opening up the former holes. What should I do?