Today I was in class typing up my notes on my ibook (g4), using microsoft word. Nothing else was open except microsoft word. After a little pause in typing I went to go back to typing again. All of a sudden, a black horizontal scrolling bar slid down the screen and the screen turned white and the scrolling bar just kept going down the screen. I tried everything to get it to work again. and then just had to hold down the power button. I lost all my work and was bewildered as to what happened? I just checked for viruses and I just verified and repaired permissions the night before and had not even used my computer between that point until i brought my ibook to class. any ideas here?