It's taken me a little while to diagnose this issue in our favorite browser #ie6.
I'm using the suckerfish script for a drop down menu and somewhere else in the page when I am using scriptaculous' Draggables or Sortables it's causing the drop down menu to flicker when you mouse over the menu items.
I'll try and put together a good test case, but has anyone come across this one before?
I'm having this same exact problem.
EDIT: By the way, I'm using Magento.