HI, you are doing tables for layouts and due to the wayyou structured, this should be happening (because you do each set of image in a seperate row and the bigger image on the left is cuasing the bottom rightish image to show up further down)
I'd lose the tables and just create it via floats. I'd wrap the images in hte left in a <div> floated left (width a width)
Then have all the images on the rightwith a width floated left as well (make this latert in the source then the left images <div>)
It should line up (assuming your width isn't too big.)
Mess with margins to perfection .