Cooper gave some testimony to the grand jury and then didn't want to give any more. It's my understanding, IANAL, that someone testifying can't pick and chose what they want to testify about. If one is called before a grand jury, one has to say what one knows or risk various contempt actions. The exception would be 5th Amendment issues (which don't apply to him or Miller in this case).
Miller is also refusing to give information to the grand jury. She's in the same boat - it doesn't matter that she didn't publish anything about Plame. Grand juries are very touchy about people refusing to testify.
At this point, it seems to me, based on my limited understanding, that Cooper and Miller aren't in trouble because they did or didn't release classified information. They're in trouble for refusing to testify before the grand jury. Whether it's a distinction without a difference is something others can argue about.
It's not yet clear whether Novak testified before the grand jury or not. I would think that he ultimately would if he hasn't already. If he didn't cooperate fully then he should end up with the same treatment if the law is to be impartial.
My $0.02. Corrections welcome.
[edit:] The 83 page .PDF of the decision today is [link|http://news.findlaw.com/wp/docs/plame/inregjmiller21505opn.pdf|here].
Cheers,
Scott.