We need to remember that last summer Joe Wilson was publicly bragging that he wanted to go down in history as the man who brought down the Bush administration. So he - and anyone involved with arranging his trip to Niger - may have been deliberately setting up the administration for this "scandal" to happen. Hence, they might be the original source of some or all of the leaks.
it's also a conflict of interests for Russert at this point - they've not had a week to cover an incredible story given the recent revelations re Wilson and the fact MTP had Wilson on twice, obviously he can't have him on anymore because of the serious legal implications (jail) but they should have somebody like Pete Williams take over for one week to get Wilson back on (as he appeared with Wolfie a couple weeks back)