Replacing An Image On A Page

On certain pages, I display 10 pictures as thumbnails and one in the center to view as the main one. It works pretty nice but its not working for me in FF .. so I have to upgrade my coding methods here.

I have named the picture in question 'swap' in the html. The command that activates the swap is here:

onClick="MM_swapImage('swap','','listings_images/#URL.ID#/#display.img1#',1)"

Which runs this:

function MM_swapImage() { //v3.0
var i,j=0,x,a=MM_swapImage.arguments; document.MM_sr=new Array; for(i=0;i<(a.length-2);i+=3)
if ((x=MM_findObj(a[i]))!=null){document.MM_sr[j++]=x; if(!x.oSrc) x.oSrc=x.src; x.src=a[i+2];}
}

Now to note, that I am not doing a rollover here, just click and swap the image.