Black Magic

Okay, this is an interesting topic. My mother has some friends who are CONSTANTLY blaming everything that goes wrong on Kala Jadu. Everytime they come over, they try to convince my mother that someone is doing Kala Jadu on her over very trivial household things. Of course, as soon as they are gone, I have to convince her to abandon these silly notions.

What is Kala Jaadu though? How can it be effective if the person is good and not harming anyone? Do Muslims believe in Kala Jaadu? I hear talk about it all the time, but no proof.

Personally, this stuff makes no sense to me. I dont like to think that anyone other then Allah (swt) has that kind of power. Furthermore, I dont like to think that mere human beings can alter the course of someone's life by chanting something and jumping over a lake backwards or something.

Can anyone shed some light on this?