Ok I created a mock button in IR. Here is the code it created:
<!-- ImageReady Preload Script (Untitled-1) -->
<script type="text/javascript">
<!--
function newImage(arg) {
if (document.images) {
rslt = new Image();
rslt.src = arg;
return rslt;
}
}
function changeImagesArray(array) {
if (document.images && (preloadFlag == true)) {
for (var i=0; i<array.length; i+=2) {
document[array[i]].src = array[i+1];
}
}
}
function changeImages() {
changeImagesArray(changeImages.arguments);
}
function toggleImages() {
for (var i=0; i<toggleImages.arguments.length; i+=2) {
if (selected == toggleImages.arguments[i]) changeImagesArray(toggleImages.arguments[i+1]);
}
}
var selected = '';
var preloadFlag = false;
function preloadImages() {
if (document.images) {
test_01_over = newImage("images/test_01-over.gif");
preloadFlag = true;
}
}
// -->
</script>
<!-- End Preload Script -->
</head>
<body bgcolor="#FFFFFF" leftmargin="0" topmargin="0" marginwidth="0" marginheight="0" onload="preloadImages();">
<!-- ImageReady Slices (Untitled-1) -->
<a href="#"
onmouseover="toggleImages('', new Array('test_01', 'images/test_01-over.gif')); return true;"
onmouseout="toggleImages('test_01', new Array('test_01', 'images/test_01-over.gif'), '', new Array('test_01', 'images/test_01.gif')); return true;"
onmousedown="toggleImages('', new Array('test_01', 'images/test_01-over.gif')); return true;"
onmouseup="selected='test_01'; changeImages('test_01', 'images/test_01-over.gif'); return true;">
<img name="test_01" src="images/test_01.gif" width="500" height="500" border="0" alt=""></a>
<!-- End ImageReady Slices -->
</body>
The bold items are the javascript that IR creates which controls how the button acts depending on mouseover, mousedown, etc.
Hope this helps!
You have the html rollover code listed but the top part I have in bold above. This bold area of code is the code that is missing from your page. When you created the rollover it saved an html file. This script is in the file at the top of the page before the body tag <body>. You also should have an image for each change in the rollover state. 
Rollover not working 
Linear Mode
