I know how bad if feels to have someone ignore your thread.
That said, AdminCP> Template Styles> Theme> Click on your theme> global.css> Edit Stylesheet: Advance Mode.
Now before you do any edits, select all and copy the css content on to notepad in case you mess up.
Search for: border-bottom or border-top (there will be more than one hit)
From there, I would change all of the boarders black or to 0px since since you have a black theme or won't notice a 1px boarder loss.
You should get something similar to this:
border-bottom: 1px solid #fff;
Edit the border-bottom to 0px (aka pixels) or change the color corresponding to that boarder (in the example above, that will be the #fff).
It should look like this:
border-bottom: 0px solid #fff;
or this (if you want the boarder black)
border-bottom: 1px solid #000;
Similarly, you can do the same with the top boarder. Since I don't know the theme details, it is hard for me to say which boarder needs to be edited, so I say, do them all.
Sorry for not being much of a help, but I am new to this whole forum thing. Just made mine 2 weeks ago... so far we are off to a nice start though.