I have manually created a menu where the submenu items should popup over the header image slide show, but they are not. The menu works correctly with an animated gif or manually added javascript slideshow (but i could get those images to rotate so i'm trying to use the built-in ATA one).

I tried using a z-index of -1 for the #imagecontainer, but that just put the slideshow behind everything including the background. I tried a couple of different z-index options, but to no avail.

Any help would be greatly appreciated. Thanks!

did you try adding a positive z-index to your menu?

Yes and it does nothing.

Adding a positive z-index on the sub level menu item works for me

You're right miles. I was putting it on .navigation not .sub-level. Thanks a bunch!