Here's a thought from another analyst:
It may have become clear to Goss that the W.H. will not allow the DOJ to pursue subpoenas or indictments in the WaPo/Mary McCarthy matter. If so, Goss may have reached the (reasonable) conclusion that he cannot succeed in rooting out leakers in the CIA if there's not going to be a serious effort at prosecution.
This is a good point.
Let's face it, the November election is six months away, and Bush and the Republicans have their hands full and then some in order to avoid losing the House and having an impeachment inquiry starting next year. From here on out, partisan survival politics is going to consume pretty much everything in Washington.
It does seem he left in a snit, doesn't it? Oh man... not good.