Yeah, some browsers handle JS better than others (I've recently ditched FF because of its flaky JS handling).
So, for FF (and I suppose IE) it takes a second or two for the JS to kick in, so in the mean time, you see the image at the top of the stack.
So, in that slideshow, the 3rd image is set to show first, so while JS is kicking in, you could set the third image to sit at the top of the stack with CSS. E.g.
<img alt="Beau Dandy" src="../../images/beau_200.jpg" style="z-index: 2" />