Salmonmac, I don't have a clue what I did. It was the first time I've ever knitted in the round. I just know it was looking pretty good - I didn't screw up the decreases and it was the first time I'd ever done those, too. And once I knitted everything over to the DPNs and continued on my way, I knitted few rows and noticed it reversed from stockinette to reverse stockinette on the outside of the hat. Not a clue what happened.
Oh, I'll probably just bind it off as is, leave it alone and start a new one. This one was only practice - I have a whole skein of cheap yarn I just use for practicing. No loss. I'll do another one and try to figure out what I did when I get to that point again. Follow the instructions more carefully for switching from circulars to DPNs. I'm a little ADHD and probably just wasn't careful enough (obviously) in following the instructions, trying to rush through.