I, too, have had a heck of a time trying to figure out this *bug*.
Last week I was trying to set up a <UL> using images for the bullets.
For some strange reason, whenever you rolled over the navigation area
(which didn't use CSS - rather it had an onMouseOver effect) the bullet
images would disappear. I pulled my hair out for a few hours trying to
re-write the CSS for the <UL>, then threw in the towel and blamed it on
Nice to know I'm not the only one having this problem!