Tuscan Bread: Kneading issues?

Hi all!

Have gotten some good advice here in the past so will see what you think about my recent attempt at Peter Reinhart's Tuscan Bread from the Bread Baker's Apprentice.  I have generally not had problems in the past getting a smooth enough dough using either hand kneading or my kitchenaid.  I tried to make the Tuscan Bread and followed the instructions in the book for mixing in the kitchenaid.  after his recommended time it was not at all as smooth as it should be--in fact the dough wasn't really being kneaded as it was really just too stuck to the dough hook.  So I figured, I'll finish it by hand, it shouldnt' take too long as it's already gotten a good amount of kneading in the machine.

As I kneaded it got better, but even after 20 minutes it was nowhere close enough!  I let it sit and re-knead it (hoping the "autolyze" woudl kick in) and while that helped as well, it still wasn't enough.  I finally gave up and just baked it but of coruse the results were not right at all--not airy but dense, which was not how it should be.  (By the way, Reinhart says you only need to knead by hand for 10 or so minutes.  I know I am out of practice hand kneading, but this was just ridiculous).

Any ideas what the problem was?  I use King Arthur flour and bread flour strength, as recommended.