Cycling images with javascript...

I've pretty much got this working but for one tiny problem...

Go to http://ns1.aetechsystems.co.uk/~white666 and click on the Contacts link on the right side of the navbar.

You should see a map on the right. The idea, as you have by now worked out, is that clicking the zoom in or zoom out buttons changes the map image.
The image displayed to start with is map 3 out of 5 and the src property is set in the HTML code. All 5 images are preloaded on page load.

To see the problem (I've only tried this in IE 6 atm) just click on one of the zoom buttons and then click the other one to go back to the starting image. Now unless it's just my browser acting out some personal vendetta against me then you'll probably find that you have to right click where the image should be and select 'Show Picture' to see it again. Obviously this is not the desired effect so any suggestions?

Oh, I noticed that if you navigate away from the page then use the back button to return then everything works fine.

I use the following JS to cycle through them...

if(!cycle){
      var cycle = 3; //Sets the starting value of cycle at page load
}

function picswap(zoom){
      var image = document.getElementById('mapimage');
      if(zoom == 'in'){
            cycle = cycle + 1;
            image.src = 'images/maps/map'+cycle+'.jpg';
      } else {
            cycle = cycle - 1;
            image.src = 'images/maps/map'+cycle+'.jpg';
      }
      if(cycle < 2){
            document.zoomin.style.display = 'inline'
            document.zoomout.style.display = 'none'
      } else if(cycle > 4){
            document.zoomin.style.display = 'none'
            document.zoomout.style.display = 'inline'
      } else {
            document.zoomin.style.display = 'inline'
            document.zoomout.style.display = 'inline'
      }
}