"Could it be he is trying to shut the investigation down before he and his cohorts get embarrassed?"
If by "shut down the investigation" you mean "revoke Rove's security clearance and hang his head on a stake out on the ellipse", then maybe. His press conference with Chuckie didn't sound much like trying to shut anything down...
I'll lay odds that J Miller is in fact protecting Ms.Plame.
Ms. Plame probably had Miller's ear after probably knowing each other on the cocktail circuit for a few years.
What if this doesn't stop with Plame? What if there is proven to be a massive concerted effort within Bush-haters in the CIA to "color" and "deceive" as Bush laid out his rationale for the Iraq invasion???
Now, that COULD be what this grand jury is trying to investigate. I don't think they give two hoots in hell about Karl Rove. This story is wwwwaaaaayyyy beyond Rove, but Wilson et al, HAVE to continue to make Rove front and center, so as to avoid any scrutiny of his/her actions.