Here's another theory. Someone who isn't being talked about much, of a lower-level than Libby / Rove, got ratted out by a reporter on providing info on Emma Peel. That person, in Fitzgerald's sites, starts singing like a bird that it was covered up by Libby / Rove et al - or worse, that he was ordered to do it. And all the rest has been trying to pin it on higher-ups - classic scandal style.
This theory does depend, necessarily, on her having covert status at some point after July 1998. And, as I've said repeatedly, none of us know whether she did or not.
CBS News chief White House correspondent John Roberts reports the prosecutor has informed targets of the investigation of his intentions and that can only mean indictments.
src: http://www.cbsnews.com/stories/2005/10/26/politics/main981236.shtml
If she did, it was a bureaucratic oversight. Aldrich Ames killed her undercover career.