I can't figure out why the top nav menu is showing wrong in IE.

http://dev.trinityriverdesign.com/optivestinc/

The hover color is correct, but the background on the li's are showing as white.

I'm also on a Mac, so troubleshooting IE is soooo difficult.

Any of you have a clue or a direction to send me to look would be appreciated!

Thanks in advance :)