It's where the laser hits the other part of the disc and starts to read from that. The first layer is where it will start and eventually it will run out. So it switches over to other layer and reads from that. The pause usually happens when the picture is black. (changing scene) you hardly notice it, but in some DVD's it very easy to spot when this pause happens.
Jumping picture? I doubt this has to be your problem. Have you tried updating your graphics drivers? How much memory do you have?