In a word, yes. Perhaps he really didn't know about the instant messages as he suggests. Perhaps the media is being too hard on the Republican leadership. Perhaps this was part of a coordinated "October Surprise" to throw Republicans off their game in the month leading up the election. It doesn't matter, if he didn't know, he should have known. Is it fair? Probably not. But this is politics and being a leader is about more than being fair. It's about being impeccable.
A question of timing
Is this an October Surprise? Was this held on to for release to counteract Karl Rove's "Treason Season" just as Republicans were starting to make gains? Its politics, I wouldn't put it past either side to pull a stunt like that. Bob Woodward's book is a great example. It was explicitly timed for the election targeting the issue that the Republicans are strong on.
If it was that, it went too early. Five weeks from now, every iota of detail will be vetted on this issue. If Denny Hastert is going to resign, he will have done it. The Republicans have time, not a lot, to figure out how to handle this. If this scandal ran 10 days before the election they'd be screwed. As it stands, they may still be screwed. However, there is still some time to kick Hastert out (after all Republicans seem to be the only party who routinely kicks out their disgraced leaders, McGreevy being a notable Democrat exception) and to find out if this was timed by Democrats in a controlled leak.