During the Diablo fight on normal last night, I was killed by big circle of flame he puts on the ground at the very instant I hit the health pool. The result was that I died, my grave was clearly visible, but Diablo and the rest of the game thought I was still alive. He beat on my grave briefly before the camera "fell through the floor" for an instant and then when the camera came back to its normal view. A dark, or all-black, version of me was standing next to Diablo and neither were moving. I had no access to the menu or any controls at this point and had to exit the game and start a new one.

This happened on a Mac.