nice_menus display inconsistent in IE 6, 7

I'm new here, so I hope I am posting in the correct place..

I am running nice_menus with Drupal 5.x and they display inconsistently in IE. If you move through the menu with your mouse and hover over the 2nd level in the dropdowns, only some of the items show up.
If anyone has any thoughts on how to fix this, it would be greatly appreciated.

Thanks!