Dreamweaver nivo slider image jumping down problem

I'm am working on my first website for a client and have a nivo slider slideshow on the home page.

The problem is the slideshow works but every now and then a random image in the slideshow will jump down showing the image behind it and when the transition continues after 4 seconds the image will jump back up to the proper position and the slideshow will continue it's cycle and on every restart the same problem continues with one of the images.

I just need to know how to keep my images from jumping.

Here is a screenshot of what it looks like.