I didn't run your code as I can't copy & paste from the code block in your example and I was too lazy to brute force the issue (silly forum software). Your issue may simply be the "javascript:" in the onClick parameter -- it's not needed.
I use jQuery everywhere. Here is the code I wrote that I think does what you are asking:
<script type="text/javascript">
function resetBusiness(_this) {
var isValid = false;
$("#sDiv :selected").each(function(i, selected){
isValid = isValid || $(selected).val().length;
});
if(isValid) {
$("#sBus :selected").each(function(i, selected){
$(selected).removeAttr("selected");
});
}
}
function resetDivision(_this) {
var isValid = false;
$("#sBus :selected").each(function(i, selected){
isValid = isValid || $(selected).val().length;
});
if(isValid) {
$("#sDiv :selected").each(function(i, selected){
$(selected).removeAttr("selected");
});
}
}
</script>