The first sign I had a problem was when my iTunes started to sound like a broken record. It just played the same note over and over. Then the e-mail I had half-written stopped letting me type into it. I tried to force quit, and nothing happened. The Mac was toast. My cursor had disappeared, and not even the famous three-finger restart would flip it back on. I had to hold down the power key until the MacBook Pro shut down all the way. After bringing it back up, not only was that e-mail gone, but the new blog template I had been working on reverted to the state I had it, around 1:30 this afternoon. I wasn't working on it for the full five hours or anything, but I definitely lost some work.
So... yeah. I'm not feeling too tech friendly right now. More tomorrow.