"Undisclosed serious illness"
I heard Kasparov interviewed about Fisher on the way home tonight.
Not being a competitive chess fan (I play but seldomly), I lost sight of Fisher after Reykjavik, and had no idea how he had crumbled, let alone in which direction. Part of the story accompanying the Kasparov interview included an excerpt of a phone call Fisher made to a Philippine radio station a few hours after the planes hit the WTC in 2001. They had to bleep some of it.