Why oh Why IE7

Why does IE7 do this
WHLR Menu in IE7

when all the other browsers do this

Firefox Gran Paradiso (20081027 nightly)
WHLR Menu Firefox Gran Paradiso (Firefox nightly)

Firefox 3.0.2 (Linux)
WHLR Menu in Firefox 3 (Linux)

Opera 9.61 (Linux)
WHLR Menu in Opera (Linux).png

Google Chrome
WHLR Menu in Google Chrome

This turns out to be a problem with IE that goes all the way back to IE6 and apparently doesn't seem to have been corrected with IE7. Just Google "css z-index ie" and you'll find a bunch of stuff on it. I'm already using a z-index: 1; CSS property to get the menu to display on top of everything else. Still no joy with IE.