KIA Braking

I came home from a trip this week and drove my wife's KIA. I noticed that when I slowed down the vehcile would jerk a little like something was out of balance. There was a high-pitch whining (squealing?) noise. If it had just been the noise I would have said brakes (pads) but the jerking is a new one. Any ideas? Oh, 65K miles, and the engine was just completely rebuilt, ALL new parts, by KIA 3K miles ago -- YOU DO NOT WANT THE DRIVE BELT TO BREAK IN THIS CAR!

Thanks in advance!
Bill