Hi Monica, the problem there looks like your main object was not a fully closed solid when you cut it - a cutting object will only leave its impression on an object sealing it up when that original object is a completely closed solid volume. If the object is an open surface it will just cut the surfaces and not know how to make the result a solid.

It looks like possibly some areas of your current model do not meet up quite close enough to join together to make a solid, I'll investigate it a little bit to see what might be wrong.

- Michael