Interesting. I was going to use a table as a last resort for the nav buttons. I wanted to steer clear of it because it's frowned upon by the CSS community if used as a layout tool and it may not validate.
So I tried the table technique and so far it separates the images in the column properly using the <style="margin-top:?px;"> property in the <img> tag. So the layout more or less looks fine on Netscapes 6, 7, 8, Foxfire, Opera 8, and IE6/Windows.
The height of the columns still don't match up in IE 5 or IE 5.5. So I decided to decrease the height of the banner in the left column by a few pixels to fit the column within the container. Now it's only the right column that sticks out of the column. I'm wondering if it's because instead of padding it, I gave it a border, and that's what makes it break out of the container in IE 5.