If no other css files have been changed, how about changing all ocurrences of this:

BORDER: #FFF 0px solid;

To this:

 BORDER-TOP: Transparent 0px solid; 
 BORDER-BOTTOM: Transparent 0px solid; 
 BORDER-LEFT: Transparent 0px solid; 
 BORDER-RIGHT: Transparent 0px solid; 

I've met with this before, but failed to document how I solved it. Thus I am only able to give suggestions and not solutions.

Furthermore I used also the reverse approach where I wanted to have a border around the items when the mouse hovers over them but doesn't show up when it's off.