Just what went wrong?

a friend of mine has been ignoring me. It's really strange. All of a sudden she's been ignoring me. I dont know what i've done wrong nor i could never think of anything that i could have said or done to upset her. Usually we chat online everytime we bump into each other at YM. I said hello many times when she's online but i got no reply. At first i thought, she must be busy. So i left online messages but i got no response from her. Later this afternoon, we both were online. I asked her what i have done wrong and why she's ignoring me, but again my words fell on deaf ears. I do not know what to do. It pisses me off cause i really don't know why i get silent treatment from her. Was she mad because i didn't came to say goodbye to her before she left Philippines? sigh...i can't keep on guessing. I wish she'd tell me, so i would know...It saddends me...