CIA Chief Porter Goss Resigns

Wow, that's pretty huge. Goss was met with a healty dose of opposition when his name was first circulated as the new potential CIA Director and that clamour followed him when he entered the position.

But why the sudden, unexpected departure now? That's very out of the ordinary for something like this to happen at the top level of an agency for this administration. Has Fitzgerald's CIA leak investigation poked into this realm? Or maybe the CIA has been doing some snooping like the NSA and Goss is getting out while he can?