What's so freakin' difficult about going into the grand jury and either telling the truth or saying you don't recall? That seems pretty simple to me. I'm amazed at the number of FReepers who are willing to give Libby a pass even if he lied to a grand jury. A lie is a lie. It's a crime. It's the law. If you don't like it, go do something to change the law (although I will oppose you). Don't blame Fitzgerald for trying to enforce the law.
A non-factual statement is not necessarily a lie.
At this point, we've only got the prosecutor's side of this. If it is a discrepancy between Libby's memory and that of media people (like Judith Miller), then I can see a number of ways that we can have different recollections.
Faulty memory, speculative statements, different opinions, etc.
Innocent until proven guilty. We haven't heard his side yet. (In fact, there aren't too many who have a grasp of what the crime is.)