using image swap behavior w/dynamic (datasource) images...how?

As I use Dw CS5 I can execute the images swap behavior beautifully using static images...i.e (mouseover thumb1 and large1 replaces main placeholder).  However, when I bind a datasource to bring up images in a database (MS Access) the page loads fine but when I mouseover the thumbs the whole table jumps profusely.  Thanks for reading.

Randy