I have spent all day on this and can not figure out which style is causing this grey line in my look and feel

http://blackwoodlimo.progressiveelement.com/

I have gone through the source and thought it was MainMenu_MenuContainer , but changing the background color does nothing. HELP!!!!!!!!!!

I think he is referring to the <hr class="divider_hr"> in his HTML.   It would appear that this is in your sites container skin.   Hide the container or remove the horizontal rule.  I would definitely remove the print functions since you are using white text.

I found out what the issue is, you can't see it anymore because I fixed it. I went back a few months in the archives to find the answer. The issue is with the MainMenu_MenuBreak, if you do not specifically put in the border attributes and set them to 0 then they appear in the menu break. Made no sense, I think it has something to do with the default css being loaded and even if you have the same attributes named, if you don't put in every detail that the default has the default will override your look.

.MainMenu_MenuBreak {
    border-bottom: #EEEEEE 0px solid;
    border-left: #EEEEEE 0px solid;
    border-top: #EEEEEE 0px solid;
    border-right: #EEEEEE 0px solid;
    background-color: transparent;
    height: 1px;
}