Issue with justified dropdown nav pills

Created by: Ddjay

<ul id="nav" class="nav nav-pills nav-justified">
 <li class="dropdown">
  <a class="dropdown-toggle" data-toggle="dropdown" href="#">  Menu <span class="caret"></span></a>
  <ul class="dropdown-menu">
    <li><a href="?tab=XXX">XXX</a></li>
    <li><a href="?tab=YYY">YYY</a></li>
    <li><a href="?tab=ZZZ">ZZZ</a></li>
  </ul>
 </li>
</ul>

Is not working correctly with Firefox 23.0.1. I have to set .dropdown-menu top and left to auto like this:

.dropdown-menu {
    top: auto;
    left: auto;
}

If I dont do that, the .dropdown-menu is at the bottom right of the page ... but it works without that on Safari, I am on a mac with Safari 7.0 and Firefox 23.0.0.1