One guess is that Stolen Honor was scheduled to be reviewed/discussed on September 9. This is the first instance of a large group of POWs against Kerry--a group that was not, contrary to what MSNBC said in the first five minutes of Hardball, a 527. Their testimony would normally be extremely difficult to discredit; so the best way not to have to discredit is not to air -- due to some other breaking story.
Reminds me of a conversation I had with some friends this last weekend "All politicians lie, both sides are making up stories, I'm going to decide who to vote for on election day". The more garbage the dems throw out there - the more skeptical the average non-informed swing voter gets and isn't able to distinguish between the left and right. This whole forged document issue will come back to haunt us if there are any more Kerry docs that surface.