Easy crochet hat, take two :)

Well, I did a hat with this pattern

http://www.headhuggers.org/patterns/cpatt01.htm

and I think it turned out fairly decent, ofr my first try. The only *real*
problem is that on the edge of the hat where the rows stop and start,
somehow I've messed up, so it sort of arches, and is longer at that part of
the hat. I know it was rows 11-27 that got me ;P I'm just not sure what I
did wrong, exactly... anybody have any ideas?? Would appreciate help

Ashley