Select dropdown menu

On this site here, is some javascript implemented for the Dealer Locator dropdown. I took over this site from another developer so don’t know much about javascript.

A strange phenomenon is that if I jump to Alabama, I can’t jump to any of the states after it. However, if I jump to say Arizona, I can then jump backwards to Alabama. Why is that?

JS code in question

<script type="text/javascript">
function MM_jumpMenu(targ,selObj,restore){ //v3.0
  if (restore) selObj.selectedIndex=0;